Wireless communication method and terminal for multi-user uplink transmission

ABSTRACT

Provided is a wireless communication terminal including a transceiver for transmitting/receiving a wireless signal and a processor for controlling an operation of the wireless communication terminal. The transceiver receives a first frame indicating information on a resource that a base wireless communication terminal allocates to a plurality of wireless communication terminals from the base wireless communication terminal, and transmits data to the base wireless communication terminal based on the first frame. The plurality of wireless communication terminals include the wireless communication terminal.

TECHNICAL FIELD

The present invention relates to a wireless communication method and awireless communication terminal for setting a broadband link.Specifically, the present invention relates to a wireless communicationmethod and a wireless communication terminal for increasing datacommunication efficiency by expanding a data transmission bandwidth of aterminal.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelessLAN technology that can provide a rapid wireless Internet service to themobile apparatuses has been significantly spotlighted. The wireless LANtechnology allows mobile apparatuses including a smart phone, a smartpad, a laptop computer, a portable multimedia player, an embeddedapparatus, and the like to wirelessly access the Internet in home or acompany or a specific service providing area based on a wirelesscommunication technology in a short range.

Institute of Electrical and Electronics Engineers (IEEE) 802.11 hascommercialized or developed various technological standards since aninitial wireless LAN technology is supported using frequencies of 2.4GHz. First, the IEEE 802.11b supports a communication speed of a maximumof 11 Mbps while using frequencies of a 2.4 GHz band. IEEE 802.11a whichis commercialized after the IEEE 802.11b uses frequencies of not the 2.4GHz band but a 5 GHz band to reduce an influence by interference ascompared with the frequencies of the 2.4 GHz band which aresignificantly congested and improves the communication speed up to amaximum of 54 Mbps by using an OFDM technology. However, the IEEE802.11a has a disadvantage in that a communication distance is shorterthan the IEEE 802.11b. In addition, IEEE 802.11g uses the frequencies ofthe 2.4 GHz band similarly to the IEEE 802.11b to implement thecommunication speed of a maximum of 54 Mbps and satisfies backwardcompatibility to significantly come into the spotlight and further, issuperior to the IEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n has been provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n has comeinto the spotlight. Among them, IEEE 802.11ac supports a wide bandwidth(80 to 160 MHz) in the 5 GHz frequencies. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11ac chipsets will supporteven operations in the 2.4 GHz band for the backward compatibility withthe existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of a radiointerface accepted by 802.11n, such as a wider radio frequency bandwidth(a maximum of 160 MHz), more MIMO spatial streams (a maximum of 8),multi-user MIMO, and high-density modulation (a maximum of 256 QAM).Further, as a scheme that transmits data by using a 60 GHz band insteadof the existing 2.4 GHz/5 GHz, IEEE 802.11ad has been provided. The IEEE802.11ad is a transmission standard that provides a speed of a maximumof 7 Gbps by using a beamforming technology and is suitable for high bitrate moving picture streaming such as massive data or non-compression HDvideo. However, since it is difficult for the 60 GHz frequency band topass through an obstacle, it is disadvantageous in that the 60 GHzfrequency band can be used only among devices in a short-distance space.

Meanwhile, in recent years, as next-generation wireless LAN standardsafter the 802.11ac and 802.11ad, discussion for providing ahigh-efficiency and high-performance wireless LAN communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless LAN environment, communication havinghigh frequency efficiency needs to be provided indoors/outdoors underthe presence of high-density stations and access points (APs) andvarious technologies for implementing the communication are required.

Especially, as the number of devices using a wireless LAN increases, itis necessary to efficiently use a predetermined channel. Therefore,required is a technology capable of efficiently using bandwidths bysimultaneously transmitting data between a plurality of stations andAPs.

DISCLOSURE Technical Problem

An object of the present invention is to provide an efficient wirelesscommunication method and wireless communication terminal.

An object of the present invention is to provide a wirelesscommunication method in which a plurality of wireless communicationterminals transmit data to one wireless communication terminalsimultaneously and a wireless communication terminal.

Technical Solution

According to an embodiment of the present invention, a wirelesscommunication terminal includes: a transceiver fortransmitting/receiving a wireless signal; and a processor forcontrolling an operation of the wireless communication terminal, whereinthe transceiver receives, from a base wireless communication terminal, afirst frame indicating information on a resource that the base wirelesscommunication terminal allocates to a plurality of wirelesscommunication terminals, wherein the plurality of wireless communicationterminals include the wireless communication terminal, and transmitsdata to the base wireless communication terminal based on the firstframe.

The transceiver may notify that data is to be transmitted to transmit asecond frame for setting a Network Allocation Vector (NAV) of a wirelesscommunication terminal located in a wireless coverage of the wirelesscommunication terminal to the base wireless communication terminal, andthe plurality of wireless communication terminals may transmit thesecond frame at the same time.

At this time, the plurality of wireless communication terminals maytransmit the second frame including the same format and the samecontents.

Specifically, the plurality of wireless communication terminals maytransmit the second frame at the same time using the same data rate andscramble seed.

Additionally, the transceiver may transmit information on a channelstate detected by the wireless communication terminal to the basewireless communication terminal.

At this time, the transceiver may transmit the information on thechannel state using an orthogonal code.

Specifically, the orthogonal code may be one arbitrarily selected from aplurality of orthogonal codes.

Additionally, the transceiver may transmit a signal modulated using theorthogonal code to the base wireless communication terminal through allchannels detected by the wireless communication terminal as idle.

Additionally, the transceiver may receive information on a channel whosestate is to be detected by the wireless communication terminal from thebase wireless communication terminal, and the processor may detect achannel state based on the information on the channel whose state is tobe detected by the wireless communication terminal.

At this time, the transceiver may receive a third frame indicating thatthe base wireless communication terminal is ready to receive data, andthe third frame may signal the information on the channel whose state isto be detected by the wireless communication terminal.

Specifically, a receiver address of the third frame indicates theinformation on the channel whose state may be to be detected by thewireless communication terminal.

Additionally, the transceiver may receive from the base wirelesscommunication terminal a fourth frame indicating whether the basewireless communication terminal completely receives data from each ofthe plurality of wireless communication terminals.

At this time, the fourth frame may indicate whether data is receivedcompletely for each sub-frequency band of a frequency band in which thefourth frame is transmitted.

Additionally, the first frame may indicate that the base wirelesscommunication terminal is ready to receive data and includes informationon a resource allocation for each of the plurality of wirelesscommunication terminals in an extension field form following a FrameCheck Sequence (FCS) field, and the FCS field may indicate whether thefirst frame includes error data.

According to an embodiment of the present invention, a base wirelesscommunication terminal includes: a transceiver fortransmitting/receiving a wireless signal; and a processor forcontrolling an operation of the wireless communication terminal, whereinthe transceiver transmits, to the plurality of wireless communicationterminals, a first frame indicating information on a resource allocatedto a plurality of wireless communication terminals.

At this time, a second frame notifying data transmission of each of theplurality of wireless communication terminals may be receivedsimultaneously from the plurality of wireless communication terminal.

Additionally, the transceiver may receive information on a channel statedetected by each of the plurality of wireless communication terminalsfrom the plurality of wireless communication terminals, and theprocessor may allocate a resource to the plurality of wirelesscommunication terminals based on the information on the channel statedetected by each of the plurality of wireless communication terminals.

Specifically, the transceiver may receive, from the plurality ofwireless communication terminals, the information on the channel statedetected by the plurality of wireless communication terminals, which ismodulated using an orthogonal code.

Additionally, the transceiver may transmit a third frame indicating thatthe base wireless communication terminal is ready to receive data, andthe third frame may signal information on a channel whose state is to bedetected by the plurality of wireless communication terminals.

According to an embodiment of the present invention, an operation methodof a wireless communication terminal includes: receiving a first frameindicating information on a resource that a base wireless communicationterminal allocates to a plurality of wireless communication terminalsfrom the base wireless communication terminal, wherein the plurality ofwireless communication terminals include the wireless communicationterminal; and transmitting data to the base wireless communicationterminal based on the first frame.

Advantageous Effects

One embodiment of the present invention provides an efficient wirelesscommunication method and wireless communication terminal.

Especially, one embodiment of the present invention provides a wirelesscommunication method in which one wireless communication terminaltransmits data to a plurality of wireless communication terminalssimultaneously and a wireless communication terminal.

DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating a wireless LAN system according to anembodiment of the present invention.

FIG. 2 is a view illustrating a wireless LAN system according to anotherembodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a stationaccording to an embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of an accesspoint according to an embodiment of the present invention.

FIG. 5 is a view illustrating a process that a station sets an accesspoint and a link according to an embodiment of the present invention.

FIG. 6 is a view illustrating a basic service set where a wirelesscommunication terminal is located according to an embodiment of thepresent invention.

FIG. 7 is a view illustrating an access point and a plurality ofstations set a NAV and transmit data through a CTS frame according to anembodiment of the present invention.

FIG. 8 is a view illustrating that when an access point according to anembodiment of the present invention does not receive a CTS frame, datais transmitted to a plurality of stations by allocating resources again.

FIG. 9 is a view illustrating that an access point and a station set upa NAV at the same time through a CTS frame according to an embodiment ofthe present invention.

FIG. 10 is a view illustrating a basic service set where a plurality ofwireless communication terminals are located according to anotherembodiment of the present invention.

FIG. 11 is a view illustrating that an access point according to anotherembodiment of the present invention generates an orthogonal code set forrandom access.

FIG. 12 is a view illustrating that a plurality of stations transmitdata to an access point using random access according to anotherembodiment of the present invention.

FIG. 13 is a view illustrating that when a plurality of stationsaccording to another embodiment of the present invention transmit datato an access point using a random access, a frequency band having aminimum unit frequency bandwidth is allocated to the plurality ofstations.

FIG. 14 is a view illustrating that when a plurality of stationsaccording to another embodiment transmit data to an access point using arandom access, any one station among a plurality of stations thatreceive any one channel does not transmit a transmission notifyingframe.

FIG. 15 is a view illustrating that when a plurality of stationsaccording to another embodiment transmit data to an access point using arandom access, all of a plurality of stations that receive any onechannel do not transmit a transmission notifying frame.

FIG. 16 is a view illustrating that an access point transmits a frameindicating a resource allocation according to an embodiment of thepresent invention.

FIG. 17 is a view illustrating that an access point according to anotherembodiment of the present invention transmits a reception ready frameand a frame indicating resource allocation without time interval.

FIG. 18 is a view illustrating that an access point according to anotherembodiment of the present invention transmits one frame in which atransmission notifying frame and a frame indicating resource allocationare integrated.

FIG. 19 is a view illustrating that when not receiving data through anyone sub-frequency band, an access point transmits an ACK frame accordingto another embodiment of the present invention.

FIG. 20 is a view illustrating that an access point according to anotherembodiment of the present invention transmits an ACK frame andillustrating the syntax of the ACK frame.

FIG. 21 is a ladder diagram illustrating operations of a first wirelesscommunication terminal and a second wireless communication terminalaccording to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstructed as limited to the embodiments set forth herein. Parts notrelating to description are omitted in the drawings in order to clearlydescribe the present invention and like reference numerals refer to likeelements throughout.

Furthermore, when it is described that one comprises (or includes orhas) some elements, it should be understood that it may comprise (orinclude or has) only those elements, or it may comprise (or include orhave) other elements as well as those elements if there is no specificlimitation.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2014-0168563, Nos. 10-2015-0002950, and Nos.10-2015-0033942 filed in the Korean Intellectual Property Office and theembodiments and mentioned items described in the respective applicationsare included in the Detailed Description of the present application.

FIG. 1 is a diagram illustrating a wireless LAN system according to anembodiment of the present invention. The wireless LAN system includesone or more basic service sets (BSS) and the BSS represents a set ofapparatuses which are successfully synchronized with each other tocommunicate with each other. In general, the BSS may be classified intoan infrastructure BSS and an independent BSS (IBSS) and FIG. 1illustrates the infrastructure BSS between them.

As illustrated in FIG. 1, the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA1, STA2, STA3, STA4, and STA5, accesspoints PCP/AP-1 and PCP/AP-2 which are stations providing a distributionservice, and a distribution system (DS) connecting the multiple accesspoints PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a radio medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, a term ‘terminal’ may beused to refer to a concept including a wireless LAN communication devicesuch as non-AP STA, or an AP, or both terms. A station for wirelesscommunication includes a processor and a transceiver and according tothe embodiment, may further include a user interface unit and a displayunit. The processor may generate a frame to be transmitted through awireless network or process a frame received through the wirelessnetwork and besides, perform various processing for controlling thestation. In addition, the transceiver is functionally connected with theprocessor and transmits and receives frames through the wireless networkfor the station.

The access point (AP) is an entity that provides access to thedistribution system (DS) via wireless medium for the station associatedtherewith. In the infrastructure BSS, communication among non-APstations is, in principle, performed via the AP, but when a direct linkis configured, direct communication is enabled even among the non-APstations. Meanwhile, in the present invention, the AP is used as aconcept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense.

A plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, a plurality of BSSsconnected through the distribution system is referred to as an extendedservice set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless LAN systemaccording to another embodiment of the present invention. In theembodiment of FIG. 2, duplicative description of parts, which are thesame as or correspond to the embodiment of FIG. 1, will be omitted.

Since a BSS3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA6 and STA7 are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA6 and STA7 may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention.

As illustrated in FIG. 3, the station 100 according to the embodiment ofthe present invention may include a processor 110, a transceiver 120, auser interface unit 140, a display unit 150, and a memory 160.

First, the transceiver 120 transmits and receives a radio signal such asa wireless LAN packet, or the like and may be embedded in the station100 or provided as an exterior. According to the embodiment, thetransceiver 120 may include at least one transmit/receive module usingdifferent frequency bands. For example, the transceiver 120 may includetransmit/receive modules having different frequency bands such as 2.4GHz, 5 GHz, and 60 GHz. According to an embodiment, the station 100 mayinclude a transmit/receive module using a frequency band of 6 GHz ormore and a transmit/receive module using a frequency band of 6 GHz orless. The respective transmit/receive modules may perform wirelesscommunication with the AP or an external station according to a wirelessLAN standard of a frequency band supported by the correspondingtransmit/receive module. The transceiver 120 may operate only onetransmit/receive module at a time or simultaneously operate multipletransmit/receive modules together according to the performance andrequirements of the station 100. When the station 100 includes aplurality of transmit/receive modules, each transmit/receive module maybe implemented by independent elements or a plurality of modules may beintegrated into one chip.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, for example, the transceiver 120, andthe like. The processor 110 controls various operations of radio signaltransmission/reception of the station 100 according to the embodiment ofthe present invention. A detailed embodiment thereof will be describedbelow.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. For example, theprocessor 110 and the transceiver 120 may be implemented while beingintegrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, for example, the user interface unit 140 and thedisplay unit 150 may be optionally provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention.

As illustrated in FIG. 4, the AP 200 according to the embodiment of thepresent invention may include a processor 210, a transceiver 220, and amemory 260. In FIG. 4, among the components of the AP 200, duplicativedescription of parts which are the same as or correspond to thecomponents of the station 100 of FIG. 2 will be omitted.

Referring to FIG. 4, the AP 200 according to the present inventionincludes the transceiver 220 for operating the BSS in at least onefrequency band. As described in the embodiment of FIG. 3, thetransceiver 220 of the AP 200 may also include a plurality oftransmit/receive modules using different frequency bands. That is, theAP 200 according to the embodiment of the present invention may includetwo or more transmit/receive modules among different frequency bands,for example, 2.4 GHz, 5 GHz, and 60 GHz together. Preferably, the AP 200may include a transmit/receive module using a frequency band of 6 GHz ormore and a transmit/receive module using a frequency band of 6 GHz orless. The respective transmit/receive modules may perform wirelesscommunication with the station according to a wireless LAN standard of afrequency band supported by the corresponding transmit/receive module.The transceiver 220 may operate only one transmit/receive module at atime or simultaneously operate multiple transmit/receive modulestogether according to the performance and requirements of the AP 200.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. The processor 210 controls variousoperations such as radio signal transmission/reception of the AP 200according to the embodiment of the present invention. A detailedembodiment thereof will be described below.

FIG. 5 is a diagram schematically illustrating a process in which a STAsets a link with an AP.

Referring to FIG. 5, the link between the STA 100 and the AP 200 is setthrough three steps of scanning, authentication, and association in abroad way. First, the scanning step is a step in which the STA 100obtains access information of BSS operated by the AP 200. A method forperforming the scanning includes a passive scanning method in which theAP 200 obtains information by using a beacon message (S101) which isperiodically transmitted and an active scanning method in which the STA100 transmits a probe request to the AP (S103) and obtains accessinformation by receiving a probe response from the AP (S105).

The STA 100 that successfully receives wireless access information inthe scanning step performs the authentication step by transmitting anauthentication request (S107 a) and receiving an authentication responsefrom the AP 200 (S107 b). After the authentication step is performed,the STA 100 performs the association step by transmitting an associationrequest (S109 a) and receiving an association response from the AP 200(S109 b).

Meanwhile, an 802.1X based authentication step (S111) and an IP addressobtaining step (S113) through DHCP may be additionally performed. InFIG. 5, the authentication server 300 is a server that processes 802.1Xbased authentication with the STA 100 and may be present in physicalassociation with the AP 200 or present as a separate server.

When data is transmitted using Orthogonal Frequency Division Modulation(OFDMA) or Multi Input Multi Output (MIMO), any one wirelesscommunication terminal may transmit data to a plurality of wirelesscommunication terminals simultaneously. Also, any one wirelesscommunication terminal may simultaneously receive data from a pluralityof wireless communication terminals.

For convenience of description, any one wireless communication terminalthat communicates simultaneously with a plurality of wirelesscommunication terminals is referred to as a first wireless communicationterminal and a plurality of wireless communication terminals thatsimultaneously communicate with the first wireless communicationterminal are referred to as a plurality of second wireless communicationterminals. In addition, the first wireless communication terminal may bereferred to as a base wireless communication terminal. In addition, thefirst wireless communication terminal may be a wireless communicationterminal that allocates a communication medium resource and performsscheduling in communication with a plurality of wireless communicationterminals. Specifically, the first wireless communication terminal mayperform the role of a cell coordinator. At this time, the first wirelesscommunication terminal may be the access point 200. In addition, thesecond wireless communication terminal may be the station 100 associatedwith the access point 200. In a specific embodiment, the first wirelesscommunication terminal may be a wireless communication terminal thatallocates a communication medium resource and performs scheduling in anindependent network, such as an ad-hoc network, which is not connectedto an external distribution service. In addition, the first wirelesscommunication terminal may be at least one of a base station, an eNB,and a transmission point TP.

It is described with reference to FIGS. 6 and 21 that any one secondwireless communication terminal transmits data to the first wirelesscommunication terminal. Specifically, it is described with reference toFIGS. 6 to 9 that a plurality of second wireless communication terminalsand a first wireless communication terminal set up a network allocationvector (NAV). At this time, the NAV is an indicator indicating a timeperiod during which a wireless communication terminal is not able toaccess a wireless medium regardless of whether a wireless medium is idleor not.

FIG. 6 is a view illustrating a basic service set where a wirelesscommunication terminal is located according to an embodiment of thepresent invention.

Due to the characteristics of a wireless network, the wirelesscommunication coverage covered by each wireless communication terminalmay be different. At this time, the wireless communication coverageindicates a range of an area where each wireless communication terminalis able to receive and transmit a wireless communication signal.Especially, even a plurality of wireless communication terminals locatedin the same BSS may have their different wireless communicationcoverage. Therefore, even a plurality of wireless communicationterminals belonging to the same BSS may receive different wirelesscommunication signals, and a range of an area where wirelesscommunication signals transmitted by the plurality of wirelesscommunication terminals are received may be different. In such a case,when data is transmitted between the wireless communication terminals,other wireless communication terminals that do not belong to thecorresponding BSS may access a frequency band used for datatransmission.

For example, in the drawing of FIG. 6, the access point AP, the firststation STA1, and the second station STA2 belong to the same BSS.However, the wireless communication signals transmitted by the firststation STA1 and the second station STA2 do not reach an area (e.g., a3rd party AP) of the wireless communication coverage of the access pointAP. Therefore, during the transmission of data from the first stationSTA1 and the second station STA2 to the access point AP, the wirelesscommunication terminal located in an area (e.g., a 3rd party AP) of thewireless communication coverage of the access point AP may access afrequency band that the first station STA1 and the second station STA2use for data transmission. Therefore, in order to prevent this, it isnecessary for the access point AP, the first station STA1, and thesecond station STA2 to set the NAV to prevent access to another wirelesscommunication terminal. Especially, when the first wirelesscommunication terminal and the plurality of second wirelesscommunication terminals communicate, it is necessary to set the NAV forthe wireless communication coverage of each of the plurality of secondwireless communication terminals. This will be described with referenceto FIGS. 7 and 9.

FIG. 7 is a view illustrating an access point and a plurality ofstations set a NAV and transmit data through a CTS frame according to anembodiment of the present invention.

The first wireless communication terminal transmits to the plurality ofsecond wireless communication terminals a reception ready frameindicating that it is ready to receive data. At this time, the firstwireless communication terminal may transmit a reception ready frame tothe plurality of second wireless communication terminals through acontention-based access using a back-off. Specifically, when a channelis idle for a predetermined time, the first wireless communicationterminal may transmit a reception ready frame to the plurality of secondwireless communication terminals. At this time, the predetermined timemay be an arbitration inter-frame space (AIFS) or a DCF inter-framespace (DIFS) defined in the 802.11 standard.

The reception ready frame may follow the RTS frame format defined by the802.11 standard. However, when the reception ready frame is in the RTSframe format, a wireless communication terminal included in the wirelesscommunication coverage of the first wireless communication terminal butnot included in the wireless communication coverage of the secondwireless communication terminal may determine that the RTS frame istimeout before the ACK frame transmission time point of the firstwireless communication terminal.

Therefore, the reception ready frame may follow the CTS frame formatdefined by the 802.11 standard. In particular, the reception ready framemay be a CTS frame in which a receiver address (RA) is an address of asecond wireless communication terminal transmitting a CTS frame. Inaddition, the RA of the reception ready frame may be a group addressindicating a plurality of second wireless communication terminals.Through transmission of the reception preparation frame, the firstwireless communication terminal sets the NAV of a wireless communicationterminal included in the wireless communication coverage of the firstwireless communication terminal.

In addition, the first wireless communication terminal transmits aresource allocation frame for signaling the resources allocated to eachof the plurality of second wireless communication terminals to theplurality of second wireless communication terminals. In a specificembodiment, the resource allocation frame and the reception ready framemay be one frame. The resource allocation frame may be referred to as atrigger frame since it triggers the data transmission of the secondwireless communication terminal. The resource allocation frame will bedescribed in detail again with reference to FIG. 16 to FIG. 18.

The second wireless communication terminal transmits to the firstwireless communication terminal a transmission notifying frame fornotifying that the data is to be transmitted. The transmission notifyingframe sets the NAV of the wireless communication terminal located in thewireless coverage of the second wireless communication terminal.Specifically, the plurality of second wireless communication terminalsmay sequentially transmit a transmission notifying frame. Specifically,the plurality of second wireless communication terminals may transmit atransmission notifying frame. Here, the predetermined time interval maybe a short inter-frame space (SIFS) frame defined by the 802.11standard. In a specific embodiment, the transmission order of theplurality of second wireless communication terminals may be the order ofthe subcarriers allocated to each of the plurality of second wirelesscommunication terminals. The transmission notifying frame may follow theformat of the CTS frame. Specifically, the RA of the CTS frame mayindicate the first wireless communication terminal. Through transmissionof the transmission notifying frame, the second wireless communicationterminal sets the NAV of the wireless communication terminal included inthe wireless communication coverage of the second wireless communicationterminal.

The second wireless communication terminal transmits data to the firstwireless communication terminal through the resource allocated to thesecond wireless communication terminal. Specifically, the secondwireless communication terminal transmits data to the first wirelesscommunication terminal after a predetermined time from transmission ofthe transmission notifying frame. At this time, the predetermined timemay be SIFS defined in the 802.11 standard.

The first wireless communication terminal that receives the datatransmits a reception completion frame indicating completion ofreception to the second wireless communication terminal that transmitsthe data. Specifically, the first wireless communication terminal maysequentially transmit the reception completion frame to each of theplurality of second wireless communication terminals. In a specificembodiment, the first wireless communication terminal may transmit thereception completion frame to each of the plurality of second wirelesscommunication terminals at predetermined intervals. At this time, thepredetermined time may be SIFS defined in the 802.11 standard. Inaddition, in a specific embodiment, the reception completion frame maybe an ACK frame.

The specific operations of the first wireless communication terminal andthe second wireless communication terminal will be described withreference to FIG. 7.

In the embodiment of FIG. 7, the access point AP receives data from eachof the first station STA1 and the second station STA2. Specifically, theaccess point AP receives data from each of the first station STA1 andthe second station STA2 through the following process.

The access point AP allocates a resource to each of the first stationSTA1 and the second station STA2.

The access point AP transmits a CTS frame having the group addressindicating the first station STA1 and the second station STA2 as an RA.Alternatively, the access point AP transmits a CTS frame having theaddress indicating the access point AP as an RA. Through this, theaccess point AP sets the NAV of a wireless communication terminallocated in the wireless communication coverage of the access point AP.

The access point AP transmits a resource allocation frame for signalinga resource allocated to each of the first station STA1 and the secondstation STA2.

The first station STA1 and the second station STA2 obtain information onfrequency bands allocated to the first station STA1 and the secondstation STA2 based on the resource allocation frame.

The first station STA1 and the second station STA2 transmit to theaccess point AP a CTS frame for notifying that the data is to besequentially transmitted. Specifically, the first station STA1 and thesecond station STA2 transmit a CTS frame to the access point AP at SIFSintervals. Through this, the first station STA1 sets the NAV of awireless communication terminal located in the wireless coverage of thefirst station STA1 and the second station STA2 sets the NAV of awireless communication terminal located in the wireless coverage of thesecond station STA2.

The first station STA1 and the second station STA2 transmit data to theaccess point AP through a resource allocated to each.

The access point AP receives data from the first station STA1 and thesecond station STA2 through the resources allocated to the first stationSTA1 and the second station STA2, respectively.

The access point AP transmits an ACK frame indicating completion ofreception to each of the first station STA1 and the second station STA2.Specifically, the access point AP transmits an ACK frame to the firststation STA1, and transmits an ACK frame to the second station STA2after SIFS.

When the second wireless communication terminal does not transmit thetransmission notifying frame to the first wireless communicationterminal, the operation of the first wireless communication terminalwill be described with reference to FIG. 8.

FIG. 8 is a view illustrating that when an access point according to anembodiment of the present invention does not receive a CTS frame, datais transmitted to a plurality of stations by allocating resources again.

The first wireless communication terminal may not receive thetransmission notifying frame from the second wireless communicationterminal after transmitting the reception ready frame and the resourceallocation frame to the second wireless communication terminal. In sucha case, the first wireless communication terminal allocates the resourceallocated to the second wireless communication terminal to anothersecond wireless communication terminal. Specifically, the first wirelesscommunication terminal transmits a reception ready frame and a resourceallocation frame to the second wireless communication terminal, andwaits for a predetermined time. If the transmission notifying frame isnot received from the second wireless communication terminal whilewaiting for a predetermined time, the first wireless communicationterminal allocates the resource allocated to the second wirelesscommunication terminal to another second wireless communicationterminal. At this time, the predetermined time is SIFS defined in the802.11 standard.

The first wireless communication terminal transmits a reception readyframe. At this time, the reception ready frame may include informationfor signaling a second wireless communication terminal that newlyreceives an allocated resource. Specifically, the first wirelesscommunication terminal may transmit a reception ready frame after apredetermined time from the preceding frame. At this time, thepredetermined time may be a PCF inter-frame space (PIFS) defined by the802.11 standard.

The first wireless communication terminal transmits to the secondwireless communication terminal a resource allocation frame includinginformation for signaling the reallocated resources.

Then, the operations of the second wireless communication terminal andthe first wireless communication terminal may be the same as thosedescribed above.

The specific operations of the first wireless communication terminal andthe second wireless communication terminal will be described withreference to FIG. 8.

In the embodiment of FIG. 8, the access point AP allocates a resource toeach of the first station STA1 and the second station STA2.

The access point AP transmits a CTS frame having the group addressindicating the first station STA1 and the second station STA2 as an RA.Alternatively, the access point AP transmits a CTS frame having theaddress indicating the access point AP as an RA. Through this, theaccess point AP sets the NAV of a wireless communication terminallocated in the wireless communication coverage of the access point AP.

The access point AP transmits a resource allocation frame for signalinga resource allocated to each of the first station STA1 and the secondstation STA2.

The first station STA1 transmits to the access point AP a CTS frame fornotifying that the data is to be transmitted. The second station STA2does not transmit to the access point AP a CTS frame for notifying thatdata is to be transmitted.

The access point AP allocates resources to the first station STA1 andthe third station STA3.

After PIFS from the CTS frame of the first station STA1, the accesspoint AP transmits a CTS frame having the group address indicating thefirst station STA1 and the third station STA3 as an RA. Alternatively,after PIFS from the CTS frame of the first station STA1, the accesspoint AP transmits a CTS frame having the address indicating the accesspoint AP as an RA. Through this, the access point AP again sets the NAVof a wireless communication terminal located in the wirelesscommunication coverage of the access point AP.

The access point AP transmits a resource allocation frame for signalinga resource allocated to each of the first station STA1 and the thirdstation STA3.

The first station STA1 and the third station STA3 sequentially transmitto the access point AP a CTS frame for notifying that the data is to betransmitted. Specifically, the first station STA1 and the third stationSTA3 transmit a CTS frame to the access point AP at SIFS intervals.Through this, the first station STA1 sets the NAV of a wirelesscommunication terminal located in the wireless coverage of the firststation STA1 and the third station STA3 sets the NAV of a wirelesscommunication terminal located in the wireless coverage of the thirdstation STA3.

The first station STA1 and the third station STA3 transmit data to theaccess point AP through a resource allocated to each.

The access point AP receives data from the first station STA1 and thethird station STA3 through the resources allocated to the first stationSTA1 and the third station STA3, respectively.

The access point AP transmits an ACK frame indicating completion ofreception to each of the first station STA1 and the third station STA3.Specifically, the access point AP transmits an ACK frame to the firststation STA1, and after SIFS, transmits an ACK frame to the thirdstation STA3.

In the embodiment illustrated through FIGS. 7 to 8, the plurality ofsecond wireless communication terminals sequentially transmittransmission notifying frames. Accordingly, as the number of the secondwireless communication terminals that transmit data to the firstwireless communication terminal increases, the time required for theplurality of second wireless communication terminals to transmit thetransmission notifying frame increases. This makes data transmissionbetween the plurality of second wireless communication terminal and thefirst wireless communication terminal ineffective. Therefore, a methodfor solving this is needed. This will be described with reference toFIG. 9.

FIG. 9 is a view illustrating that an access point and a station set upa NAV at the same time through a CTS frame according to an embodiment ofthe present invention.

The plurality of second wireless communication terminals may transmit atransmission notifying frame to the first wireless communicationterminal at the same time. Specifically, the plurality of secondwireless communication terminals may simultaneously transmit thetransmission notifying frame including the same format and the samecontents. At this time, the transmission address of the transmissionnotifying frame may be a group address indicating a plurality of secondwireless communication terminals.

In addition, the plurality of second wireless communication terminalsmay simultaneously transmit the transmission notifying frame using thesame data rate and scramble seed. Specifically, the plurality of secondwireless communication terminals may simultaneously transmit atransmission notifying frame based on a Modulation & Coding Scheme (MCS)or a data rate of a reception ready frame. In another specificembodiment, the plurality of second wireless communication terminals maysimultaneously transmit the transmission notifying frame based on theMCS or the data rate of the resource allocation frame. In such a case,even if the plurality of second wireless communication terminalssimultaneously transmit the transmission notifying frame, collision doesnot occur between transmission notifying frames.

The transmission notifying frame may be in a format receivable by alegacy wireless communication terminal that does not support anembodiment of the present invention. Therefore, the second wirelesscommunication terminal may transmit the transmission notifying framethrough the frequency band having the minimum unit frequency bandwidth.At this time, the minimum unit frequency bandwidth represents a minimumbandwidth used by the first wireless communication terminal.Specifically, the second wireless communication terminal may have afrequency band allocated to the second wireless communication terminaland transmit the transmission notifying frame through the frequency bandhaving the minimum unit frequency band. In another specific embodiment,the second wireless communication terminal may transmit a transmissionnotifying frame through a primary channel having a minimum unitfrequency bandwidth. In a specific embodiment, the minimum unitfrequency bandwidth may be 20 MHz. In a specific embodiment, thetransmission notifying frame may be a CTS frame. In addition, a CTSframe transmitted by a plurality of second wireless communicationterminals at the same time may be referred to as a simultaneous CTSframe. Alternatively, a CTS frame transmitted by a plurality of secondwireless communication terminals at the same time may be referred to asa duplicated CTS frame.

Through such an operation, the plurality of second wirelesscommunication terminals may set the NAV of a wireless communicationterminals located in the wireless communication coverage of each of theplurality of second wireless communication terminals. In addition, itmay reduce the time for transmitting a transmission notifying frame toset the NAV. Further, even if the number of the second wirelesscommunication terminals is increased, the time required to transmit thetransmission notifying frame does not increase.

Since the plurality of second wireless communication terminals transmitthe same transmission notifying frame, the first wireless communicationterminal may not know which of the plurality of second wirelesscommunication terminals transmits the transmission notifying frame.Accordingly, even if any one of the plurality of second wirelesscommunication terminals does not transmit the transmission notifyingframe, the first wireless communication terminal may not allocate thefrequency band allocated to the second wireless communication terminalto another second wireless communication terminal or reset the NAV of acorresponding frequency band.

Other than that, the operations of the first wireless communicationterminal and the second wireless communication terminal may be the sameas those described above.

The specific operations of the first wireless communication terminal andthe second wireless communication terminal will be described withreference to FIG. 9.

In the embodiment of FIG. 9, the access point AP receives data from eachof the first station STA1 and the second station STA2. Specifically, theaccess point AP receives data from each of the first station STA1 andthe second station STA2 through the following process.

The access point AP allocates a resource to each of the first stationSTA1 and the second station STA2.

The access point AP transmits a CTS frame having the group addressindicating the first station STA1 and the second station STA2 as an RA.Through this, the access point AP sets the NAV of a wirelesscommunication terminal located in the wireless communication coverage ofthe access point AP.

The access point AP transmits a resource allocation frame for signalinga resource allocated to each of the first station STA1 and the secondstation STA2.

The first station STA1 and the second station STA2 obtain information ona resource allocated to the first station STA1 and the second stationSTA2 based on the resource allocation frame.

The first station STA1 and the second station STA2 transmit to theaccess point AP a CTS frame for notifying that the data is to betransmitted simultaneously. As described above, the transmission addressof the CTS frame may be a group address indicating a group including thefirst station STA2 and the second station STA2. In addition, the firststation STA1 and the second station STA2 transmit the CTS frame to theaccess point AP using the same data rate and the scramble seed. Thefirst station STA1 sets the NAV of a wireless communication terminallocated in the wireless coverage of the first station STA1 and thesecond station STA2 sets the NAV of a wireless communication terminallocated in the wireless coverage of the second station STA2.

The first station STA1 and the second station STA2 transmit data to theaccess point AP through a resource allocated to each.

The access point AP receives data from the first station STA1 and thesecond station STA2 through the resources allocated to the first stationSTA1 and the second station STA2, respectively.

The access point AP transmits an ACK frame indicating completion ofreception to each of the first station STA1 and the second station STA2.Specifically, the access point AP transmits an ACK frame to the firststation STA1, and after SIFS, transmits an ACK frame to the secondstation STA2.

It is described with reference to FIGS. 10 to 15 that how the firstwireless communication terminal allocates a resource to the plurality ofsecond wireless communication terminals.

FIG. 10 is a view illustrating a basic service set where a plurality ofwireless communication terminals are located according to anotherembodiment of the present invention.

Since the wireless communication coverage of each wireless communicationterminal is different, the channel state detected by the first wirelesscommunication terminal and the plurality of second wirelesscommunication terminals may be different. Therefore, when the firstwireless communication terminal allocates a channel to each of theplurality of second wireless communication terminals in consideration ofonly the channel state detected by the first wireless communicationterminal, the first wireless communication terminal may allocate to thesecond wireless communication terminal a channel in which a collisionwith a wireless communication terminal outside the wirelesscommunication coverage of the first wireless communication terminal mayoccur. Such a situation will be described with reference to theembodiment of FIG. 16.

In the embodiment of FIG. 10, the access point AP detects the primarychannel Primary, the first secondary channel Secondary 1, the secondsecondary channel Secondary 2, and the sixth secondary channel Secondary6 as idle channels. However, the first station STA1 detects the primarychannel Primary, the fourth secondary channel Secondary 4, the fifthsecondary channel Secondary 5, and the sixth secondary channel Secondary6 as idle channels. In addition, the second station STA2 detects theprimary channel Primary, the first secondary channel Secondary 1, thefifth secondary channel Secondary 5, the sixth secondary channelSecondary 6, and the seventh secondary channel Secondary 7 as idlechannels. In addition, the third station STA3 detects the primarychannel Primary, the first secondary channel Secondary 1, the secondsecondary channel Secondary 2, the fifth secondary channel Secondary 5,and the sixth secondary channel Secondary 6 as idle channels. Inaddition, the fourth station STA4 detects the primary channel Primary,the first secondary channel Secondary 1, the second secondary channelSecondary 2, the third secondary channel Secondary 3, and the seventhsecondary channel Secondary 7 as idle channels.

At this point, when the access point AP allocates the first secondarychannel Secondary 1 to the first station STA1, allocates the secondsecondary channel Secondary 2 to the second station STA2, allocates theprimary channel Primary to the third station STA3, and allocates thesixth secondary channel Secondary 6 to the fourth station STA4, theremaining stations except for the third station STA3 may not use theallocated channels. In order to prevent such a situation, the firstwireless communication terminal should allocate a frequency band to eachof the plurality of second wireless communication terminals inconsideration of the channel state detected by each of the plurality ofsecond wireless communication terminals. Specifically, the secondwireless communication terminal may transmit information on the channelstate detected by the second wireless communication terminal, and thefirst wireless communication terminal may allocate a frequency band tothe second wireless communication terminal based on the received channelstate information. This will be described with reference to FIGS. 11 to15.

FIG. 11 is a view illustrating that an access point according to anotherembodiment of the present invention generates an orthogonal code set forrandom access.

When using a code having orthogonal properties, a plurality of wirelesscommunication terminals may simultaneously transmit different frames toany one wireless communication terminal. Therefore, if using this, aplurality of second wireless communication terminals may simultaneouslytransmit information on the channel state detected by the plurality ofsecond wireless communication terminals to the first wirelesscommunication terminal.

Specifically, one BSS may set an orthogonal code set to which aplurality of second wireless communication terminals are able to access.Accordingly, the second wireless communication terminal may access thefirst wireless communication terminal by using any one orthogonal codein the orthogonal code set. In a specific embodiment, a different basesequence than an adjacent BSS is allocated to a BSS. For example, theplurality of base sequences may be allocated to the plurality of BSSs,respectively. In each of a plurality of BSSs, the first wirelesscommunication terminal and the second wireless communication terminalmay generate a plurality of orthogonal codes included in the orthogonalcode set based on the allocated base sequence. Specifically, the firstwireless communication terminal and the second wireless communicationterminal may generate a plurality of orthogonal codes included in theorthogonal code set by cyclic-shifting the allocated base sequence.

Specifically, the first wireless communication terminal and the secondwireless communication terminal may receive an index indicating a basesequence. At this time, the first wireless communication terminal andthe second wireless communication terminal may obtain a base sequenceaccording to the index indicating the base sequence. Thereafter, thefirst wireless communication terminal and the second wirelesscommunication terminal may generate a plurality of orthogonal codesincluded in the code set using the base sequence obtained according tothe length of a predetermined base sequence and the size of a cyclicshift.

When the BSS uses eight channels in a 20 MHz unit, the length of thebase sequence may be eight or more. The length of the base sequence maybe longer for stable zero auto-correlation characteristics. Throughthis, the first wireless communication terminal and the second wirelesscommunication terminal may minimize base sequence interference betweenadjacent BSSs.

In a specific embodiment, the base sequence may be generated by aZadoff-Chu sequence that satisfies Constant Amplitude Zero AutoCorrelation (CAZAC) characteristics.

Specifically, the second wireless communication terminal may arbitrarilyselect any one orthogonal code from the generated orthogonal code setand use the selected orthogonal code as a multiple access code. Inanother specific embodiment, the second wireless communication terminalmay use a fixed orthogonal code. Specifically, the fixed orthogonal codemay be allocated to the second wireless communication terminal when thefirst wireless communication terminal associates with the secondwireless communication terminal. Alternatively, the fixed orthogonalcode may be allocated to the second wireless communication terminalagain when the first wireless communication terminal associates with thesecond wireless communication terminal again. At this time, the fixedorthogonal code may be obtained by calculating the identifier of thesecond wireless communication terminal with the size and module of theorthogonal code set. At this time, the identifier of the second wirelesscommunication terminal may be an AID for identifying the association ofthe first wireless communication terminal and the second wirelesscommunication terminal.

When a plurality of second wireless communication terminals areconnected using different orthogonal codes, orthogonality is maintainedbetween orthogonal codes. Accordingly, the first wireless communicationterminal may know by what code the second wireless communicationterminal accesses through the auto-correlation operation with respect tothe base sequence. Especially, when the CAZAC sequence is used, thenumber of codes included in the code set increases as the length of thebase sequence increases. Accordingly, the probability of codeoverlapping between wireless communication terminals is also reduced.

It is described with reference to FIGS. 12 to 15 that how a plurality ofsecond wireless communication terminals transmit the idle state of afrequency band to the first wireless communication terminal using suchan orthogonal code.

FIG. 12 is a view illustrating that a plurality of stations transmitdata to an access point using random access according to anotherembodiment of the present invention.

When the first wireless communication terminal transmits a frameindicating reception preparation, the second wireless communicationterminal transmits a signal modulated using an orthogonal code to thefirst wireless communication terminal through all the channels detectedas idle state. At this time, the first wireless communication terminalmay arbitrarily select any one of a plurality of orthogonal codesincluded in the orthogonal code set. In another specific embodiment, aplurality of orthogonal codes may be allocated to the plurality ofsecond wireless communication terminals, respectively.

In a specific embodiment, the first wireless communication terminal maysignal a channel whose idle state should be determined by the secondwireless communication terminal through a reception ready frame.Specifically, the first wireless communication terminal may signal achannel whose idle state should be determined by the second wirelesscommunication terminal through a reception ready frame. For example, theRA of the reception ready frame may indicate a combination of channelswhose idle state should be determined by the second wirelesscommunication terminal. At this time, the second wireless communicationterminal receives a reception ready frame and performs CCA only for thechannel signaled by the reception ready frame. Therefore, the secondwireless communication terminal normally may detect only the primarychannel Primary Channel, and perform a clear channel assessment (CCA)only on the channel signaled by a reception ready frame when thereception ready frame is received. Through this, unnecessary channeldetecting operation of the second wireless communication terminal may bereduced.

The first wireless communication terminal decodes a signal transmittedthrough each channel to extract an orthogonal code.

The first wireless communication terminal allocates resources to theplurality of second wireless communication terminals based on theextracted orthogonal code. Specifically, the first wirelesscommunication terminal allocates a frequency band to the plurality ofsecond wireless communication terminals based on the extractedorthogonal code. At this time, the first wireless communication terminalmay allocate a frequency band smaller than the minimum unit frequencybandwidth to the second wireless communication terminal. At this time,the first wireless communication terminal may allocate a frequency bandhaving a bandwidth of 5 MHz to the second wireless communicationterminal.

The first wireless communication terminal transmits a resourceallocation frame for signaling the resources allocated to each of theplurality of second wireless communication terminals. The first wirelesscommunication terminal transmits the resource allocation frame throughthe frequency band allocated to the second wireless communicationterminal. At this time, if the frequency band allocated to each of theplurality of second wireless communication terminals is smaller than theminimum unit frequency band, the first wireless communication terminalmay transmit the resource allocation frame to the second wirelesscommunication terminal through the frequency band having a frequencybandwidth smaller than the minimum unit frequency bandwidth. In aspecific embodiment, the first wireless communication terminal maytransmit a resource allocation frame to the second wirelesscommunication terminal through a frequency band having a minimumfrequency bandwidth allocable to the second wireless communicationterminal. The minimum frequency bandwidth that the first wirelesscommunication terminal is able to allocate to the second wirelesscommunication terminal may be the smallest unit of the sub-carrierblock.

The resource allocation frame may include information on the orthogonalcode transmitted by the second wireless communication terminal allocatedto the frequency band in which the resource allocation frame istransmitted. Specifically, the information on the orthogonal code may bean orthogonal code index indicating the orthogonal code.

When the orthogonal code is fixedly allocated to the second wirelesscommunication terminal, the resource allocation frame may include anidentifier for identifying the second wireless communication terminalallocated to the frequency band in which the resource allocation frameis transmitted. This is because, when the orthogonal code is fixedlyallocated to the second wireless communication terminal, the firstwireless communication terminal may identify the second wirelesscommunication terminal that transmits the extracted orthogonal code. Atthis time, the identifier may be a MAC address of the second wirelesscommunication terminal.

The second wireless communication terminal may extract the informationon the orthogonal code or the identifier for identifying the secondwireless communication terminal from the resource allocation frame todetermine the frequency band allocated to the second wirelesscommunication terminal.

The second wireless communication terminal may transmit a transmissionnotifying frame to the first wireless communication terminal. The secondwireless communication terminal sets the NAV of a wireless communicationterminal located in the wireless communication coverage of the secondwireless communication terminal. At this time, the plurality of secondwireless communication terminals may simultaneously transmittransmission notifying frames to the first wireless communicationterminal as described above. At this time, the transmission notifyingframe may be a simultaneous CTS frame.

The second wireless communication terminal transmits data to the firstwireless communication terminal through the frequency band allocated tothe second wireless communication terminal.

The first wireless communication terminal, which receives data,transmits a reception completion frame to the second wirelesscommunication terminal that transmits the data. At this time, the firstwireless communication terminal may transmit the reception completionframe to the second wireless communication terminal through thefrequency band having the frequency bandwidth smaller than the minimumunit frequency bandwidth. In a specific embodiment, the first wirelesscommunication terminal may transmit a reception completion frame to eachof the plurality of second wireless communication terminals for eachfrequency band allocated to each of the plurality of second wirelesscommunication terminals through OFDMA. At this time, the frequency bandallocated to the second wireless communication terminal may be theminimum frequency bandwidth that the first wireless communicationterminal is able to allocate to the second wireless communicationterminal. Specifically, the minimum frequency bandwidth that the firstwireless communication terminal is able to allocate to the secondwireless communication terminal may be the smallest unit of thesub-carrier block.

Also, the first wireless communication terminal may transmit thereception completion frame for each minimum frequency bandwidth that thefirst wireless communication terminal is able to allocate to the secondwireless communication terminal. In such a case, the receptioncompletion frame may indicate that data is received through thefrequency band in which the reception completion frame is transmitted.

However, when the first wireless communication terminal transmits areception completion frame through the frequency band having thefrequency bandwidth smaller than the minimum unit frequency bandwidth, alegacy wireless communication terminal that does not support anembodiment of the present invention may not receive the receptioncompletion frame. Accordingly, this may cause an issue in the operationof the legacy wireless communication terminal. For example, in the802.11 standard, a wireless communication terminal accesses acorresponding channel when the channel is idle during AIFS or DIFS.However, if an ACK frame indicating reception completion is not receivedat the time point when the NAV of the wireless communication terminalends, the wireless communication terminal accesses the channel when thechannel is idle during EIFS longer than DIFS. Therefore, when the firstwireless communication terminal transmits a reception completion framethrough a frequency band having a frequency bandwidth smaller than theminimum unit frequency bandwidth, a legacy wireless communicationterminal waits for EIFS instead of DIFS during back-off. Accordingly,the legacy wireless communication terminal is more disadvantageous thanthe wireless communication terminal in contention-based access accordingto an embodiment of the present invention.

Therefore, when the first wireless communication terminal transmits thereception completion frame through the frequency band having thefrequency bandwidth smaller than the minimum unit frequency bandwidth,the first wireless communication terminal may re-transmit the receptioncompletion frame through the frequency band having the minimum unitfrequency bandwidth. At this time, the first wireless communicationterminal may transmit the reception completion frame in which the RAindicates the first wireless communication terminal. In another specificembodiment, the first wireless communication terminal may transmit areception completion frame, which is a group address that the RAindicates a group including a plurality of second wireless communicationterminals. At this time, the first wireless communication terminal maytransmit a reception completion frame to the plurality of secondwireless communication terminals for each minimum unit frequencybandwidth. Specifically, the first wireless communication terminal maytransmit a reception completion frame for a plurality of second wirelesscommunication terminals that receive the corresponding allocated minimumunit frequency bandwidth for each minimum frequency bandwidth. Forexample, it is assumed that a primary channel is allocated to a firststation and a second station, and a first secondary channel is allocatedto a third station and a fourth station. In such a case, the accesspoint transmits a reception completion frame indicating receptioncompletion for data transmitted by the first station and the secondstation through the primary channel, and transmits a receptioncompletion frame indicating reception completion for data transmitted bythe third station and the fourth station through the first secondarychannel. Through such an operation, compatibility with a legacy wirelesscommunication terminal that does not support a frequency bandwidthsmaller than the minimum unit frequency bandwidth may be secured.

The specific operations of the first wireless communication terminal andthe second wireless communication terminal will be described withreference to FIG. 12.

In the embodiment of FIG. 12, the access point AP transmits a CTS framehaving the group address indicating the first station STA1 to the eighthstation STA8 as an RA. Through this, the access point AP sets the NAV ofa wireless communication terminal located in the wireless communicationcoverage of the access point AP.

The first station STA1 to the eighth station STA8 detect whether thechannel is idle. As described above, the access point AP may signal achannel whose idle state should be detected by the first station STA1 tothe eighth station STA8 through the RA value of the CTS frame. At thistime, the first station STA1 to the eighth station STA8 may detect theidle state of the channel signaled by the CTS frame. In FIG. 12, the CTSframe signals the primary channel Primary, the first secondary channelSecondary 1, the second secondary channel Secondary 2, and the thirdsecondary channel Secondary 3, and the first station STA1 to the eighthstation STA8 perform a CCA on the primary channel Primary, the firstsecondary channel Secondary 1, the second secondary channel Secondary 2,and the third secondary channel Secondary 3.

The first station STA1 to the eighth station STA8 transmit signals tothe access point AP using orthogonal codes through all channels detectedas idle. The first station STA1 and the second station STA2 detect thatthe primary channel Primary, the first secondary channel Secondary 1,the second secondary channel Secondary 2, and the third secondarychannel Secondary 3 are idle. Therefore, the first station STA1 and thesecond station STA2 transmit orthogonal codes to the access point APthrough the primary channel Primary, the first secondary channelSecondary 1, the second secondary channel Secondary 2, and the thirdsecondary channel Secondary 3. The third station STA3 detects that theprimary channel Primary and the first secondary channel Secondary 1 areidle. Therefore, the third station STA3 transmits orthogonal codes tothe access point AP through the primary channel Primary and the firstsecondary channel Secondary 1. The fourth station STA4 detects that theprimary channel Primary is idle. Therefore, the third station STA3transmits orthogonal codes to the access point AP through the primarychannel Primary. The fifth station STA5 detects that the primary channelPrimary and the first secondary channel Secondary 1 are idle. Therefore,the fifth station STA5 transmits orthogonal codes to the access point APthrough the primary channel Primary and the first secondary channelSecondary 1. The sixth station STA6 detects that the primary channelPrimary, the second secondary channel Secondary 2, and the thirdsecondary channel Secondary 3 are idle. Therefore, the sixth stationSTA6 transmits orthogonal codes to the access point AP through theprimary channel Primary, the second secondary channel Secondary 2, andthe third secondary channel Secondary 3. The seventh station STA7detects that the primary channel Primary, the first secondary channelSecondary 1, and the second secondary channel Secondary 2 are idle. Theseventh station STA7 transmits orthogonal codes to the access point APthrough the primary channel Primary, the first secondary channelSecondary 1, and the second secondary channel Secondary 2. The eighthstation STA8 detects that the primary channel Primary and the secondsecondary channel Secondary 2 are idle. The eighth station STA8transmits orthogonal codes to the access point AP through the primarychannel Primary and the second secondary channel Secondary 2.

At this time, the orthogonal codes of the first station STA1 to theeighth station STA8 are all different. Also, as described above, each ofthe first station STA1 to the eighth station STA8 may arbitrarily selectany one orthogonal code from orthogonal code set including a pluralityof orthogonal codes. In another specific embodiment, a plurality oforthogonal codes may be allocated to the first station STA1 to theeighth station STA8, respectively.

The access point AP extracts an orthogonal code from the transmittedsignal.

The access point AP allocates a resource to each of the first stationSTA1 and the second station STA2 based on the extracted orthogonal code.

The access point AP transmits an sCTS frame for signaling resourcesallocated to each of the first station STA1 to the eighth station STA8.In a specific embodiment, the first wireless communication terminal maytransmit a resource allocation frame to the second wirelesscommunication terminal through a frequency band having a minimumfrequency bandwidth allocable to the second wireless communicationterminal. The minimum frequency bandwidth that the first wirelesscommunication terminal is able to allocate to the second wirelesscommunication terminal may be the smallest unit of the sub-carrierblock.

The first station STA1 to the eighth station STA8 extract information onthe orthogonal code or identifiers for identifying the first stationSTA1 to the eighth station STA8 from the sCTS frame to determine afrequency band allocated to each of the first station STA1 to the eighthstation STA8.

Each of the first station STA1 to the eighth station STA8 transmits asimultaneous CTS frame to the first wireless communication terminal. Thefirst station STA1 to the eighth station STA8 set the NAV of a wirelesscommunication terminal located in the wireless communication coverage ofthe first station STA1 to the eighth station STA8. The first stationSTA1 to the eighth station STA8 transmit data through a frequency bandhaving a minimum unit frequency bandwidth.

Each of the first station STA1 to the eighth station STA8 transmits datato the first wireless communication terminal through a frequency bandallocated to each of the first station STA1 to the eighth station STA8.

The access point AP transmits an sACK frame indicating receptioncompletion to each of the first station STA1 to the eighth station STA8through the frequency band having the minimum frequency bandwidthallocable to each of the first station STA1 to the eighth station STA8.

The access point AP transmits an ACK frame through a frequency bandhaving a minimum unit frequency bandwidth. At this time, the accesspoint AP may transmit an ACK frame in which the RA indicates the accesspoint AP. In another specific embodiment, an access point AP maytransmit an ACK frame, which is a group address that the RA indicates agroup including a plurality of stations. In a specific embodiment, theaccess point AP may transmit an ACK frame for the fourth station STA4and the fifth station STA5 through the primary channel Primary. Also,the access point AP may transmit an ACK frame for the third station STA3and the seventh station STAT through the first secondary channelSecondary 1. Also, the access point AP may transmit an ACK frame for thefirst station STA1 and the eighth station STA8 through the secondsecondary channel Secondary 2. Also, the access point AP may transmit anACK frame for the second station STA2 and the sixth station STA6 throughthe third secondary channel Secondary 3.

FIG. 13 is a view illustrating that when a plurality of stationsaccording to another embodiment of the present invention transmit datato an access point using a random access, a frequency band having aminimum unit frequency bandwidth is allocated to the plurality ofstations.

When the first wireless communication terminal allocates a frequencyband to the plurality of second wireless communication terminals in aunit of the minimum frequency bandwidth, the first wirelesscommunication terminal may transmit a resource allocation frame to eachof the plurality of second wireless communication terminals.

In addition, when the first wireless communication terminal allocates afrequency band to the plurality of second wireless communicationterminals in a unit of the minimum frequency bandwidth, the firstwireless communication terminal may transmit a reception completionframe to each of the plurality of second wireless communicationterminals. When the first wireless communication terminal transmits thereception completion frame through the frequency band having the minimumunit frequency bandwidth, a legacy wireless communication terminalsupporting only the minimum unit frequency bandwidth or more may receivethe reception completion frame. Therefore, the first wirelesscommunication terminal does not need to transmit the receptioncompletion frame again.

However, as described above, the first wireless communication terminalmay transmit a reception completion frame to each of the plurality ofsecond wireless communication terminals for each frequency bandallocated to each of the plurality of second wireless communicationterminals through OFDMA. In such a case, the first wirelesscommunication terminal may transmit one physical frame transmittedthrough a frequency bandwidth greater than the minimum unit frequencybandwidth. At this time, the first wireless communication terminal maytransmit the reception completion frame for any one second wirelesscommunication terminal by the minimum unit frequency bandwidth throughthe lower physical frame. In such a case, the legacy wirelesscommunication terminal may not receive the reception completion frame.

The specific operations of the first wireless communication terminal andthe second wireless communication terminal will be described withreference to FIG. 13.

In the embodiment of FIG. 13, operations until the first station STA1 tothe fourth station STA4 transmit orthogonal codes to the access point APare the same as those of the embodiment of FIG. 12. However, the accesspoint AP allocates a frequency band having a minimum unit frequencybandwidth to each of the first station STA1 to the fourth station STA4.

Therefore, the access point AP transmits an sCTS frame for signaling aresource allocation to each of the first station STA1 to the fourthstation STA4 through the frequency band having the minimum unitfrequency bandwidth.

Each of the first station STA1 to the fourth station STA4 transmits datato the access point AP through an allocated frequency band.

The access point AP transmits data to the first station STA1 to thefourth station STA4 through the frequency band allocated to each of thefirst station STA1 to the fourth station STA4.

FIG. 14 is a view illustrating that when a plurality of stationsaccording to another embodiment transmit data to an access point using arandom access, any one of a plurality of stations receiving any oneallocated channel is not able to transmit a transmission notifyingframe.

As described above, the plurality of second wireless communicationterminals may simultaneously transmit the transmission notifying frameincluding the same format and the same contents. In such a case, even ifthe first wireless communication terminal receives the transmissionnotifying frame, the first wireless communication terminal may not knowwhich second wireless communication terminal transmits the transmissionnotifying frame. Therefore, even if any one wireless communicationterminal that does not receive an allocated sub-frequency band includedin the same frequency band does not transmit the transmission notifyingframe, the first wireless communication terminal may not take a separateaction. This will be described in detail with reference to FIG. 14.

In the embodiment of FIG. 14, the seventh station STA7 and the thirdstation STA3 receive the allocated first secondary channel Secondary 1.However, the frequency band allocated to the seventh station STA7 isbeing used by another wireless communication terminal before the seventhstation STA transmits the transmission notifying frame. Therefore, theseventh station STAT may not transmit the transmission notifying frame.The operations of the first station STA1 to the sixth station STA6, theeighth STAB, and the access point AP are the same as those of theembodiment described with reference to FIG. 12.

However, if all of the second wireless communication terminals thatreceive an allocated sub-frequency band included in any one frequencyband (channel) are not able to transmit a transmission notifying frame,the first wireless communication terminal determine that thecorresponding frequency band cannot be used. Accordingly, the firstwireless communication terminal may perform additional operationsthereon. This will be described with reference to FIG. 15.

FIG. 15 is a view illustrating that when a plurality of stationsaccording to another embodiment transmit data to an access point using arandom access, all of a plurality of stations receiving any oneallocated channel are not able to transmit a transmission notifyingframe.

If there is a frequency band in which the first wireless communicationterminal does not receive the transmission notifying frame, the firstwireless communication terminal may reset the NAV set in thecorresponding frequency band. Specifically, if there is a frequency bandin which the first wireless communication terminal does not receive thetransmission notifying frame, the first wireless communication terminalmay transmit the NAV reset frame indicating that the NAV set in thefrequency band in which the frame is transmitted through thecorresponding frequency band. Specifically, if all of the secondwireless communication terminals to which sub-frequency bands includedin any one frequency band are not allocated, are not able to transmitthe transmission notifying frame, the first wireless communicationterminal may transmit the NAV reset frame through the correspondingfrequency band.

In addition, when there is a frequency band not allocated to the secondwireless communication terminal, the first wireless communicationterminal may reset the NAV set in the corresponding frequency band.Specifically, when there is a frequency band that is not allocated tothe second wireless communication terminal, the first wirelesscommunication terminal may transmit the NAV reset frame through thecorresponding frequency band.

In a specific embodiment, the NAV reset frame indicating the resettingof the NAV set in the frequency band in which the frame is transmittedmay be a CF-END frame.

The specific operations of the first wireless communication terminal andthe second wireless communication terminal will be described withreference to FIG. 15.

In the embodiment of FIG. 15, the access point AP allocates frequencybands to the second station STA2 to the seventh station STA7.Specifically, the access point AP allocates the primary channel Primaryto the fourth station STA4 and the fifth station STA5, allocates thefirst secondary channel Secondary 1 to the third station STA3 and theseventh station STA7, and allocates the third secondary channelSecondary 3 to the second station STA2 and the sixth station STA6.

The access point AP transmits the CF-END frame to the second secondarychannel Secondary 2 that is not allocated to any station. Through this,the access point AP resets the NAV for the second secondary channelSecondary 2 set to a wireless communication terminal located in thewireless communication coverage of the access point AP by a CTS-to-STAgroup frame indicating reception preparation.

The access point AP does not receive any Simulated CTS frame through thefirst secondary channel Secondary 1.

Therefore, the access point AP transmits the CF-END frame to the firstsecondary channel Secondary 1. Through this, the access point AP resetsthe NAV for the first secondary channel Secondary 1 set to a wirelesscommunication terminal located in the wireless communication coverage ofthe access point AP by a CTS-to-STA group frame indicating receptionpreparation.

The other operations of the access point AP, the second station STA2,and the fourth station STA4 to the sixth station STA6 are the same asthose of the embodiment of FIG. 12.

Through such an operation, the first wireless communication terminal mayquickly return an unused frequency band to another wirelesscommunication terminal.

Through the operations of the first wireless communication terminal andthe second wireless communication terminal described with reference toFIGS. 10 to 15, the first wireless communication terminal may allocateresources to the plurality of second wireless communication terminals inconsideration of the state of the channel located outside the wirelesscommunication coverage of the first wireless communication terminal. Inaddition, it is possible to quickly return the frequency band not usedby the first wireless communication terminal, thereby enhancingcoexistence efficiency with other BSSs.

As described above, in order for the plurality of second wirelesscommunication terminals to transmit data to the first wirelesscommunication terminal, the first wireless communication terminalallocates a resource including a frequency band to each of the pluralityof second wireless communication terminals. Then, the first wirelesscommunication terminal should signal the frequency band allocated toeach of the plurality of second wireless communication terminals. Amethod for signaling the frequency band allocated to each of theplurality of second wireless communication terminals will be describedwith reference to FIGS. 16 to 18.

FIG. 16 is a view illustrating that an access point transmits a frameindicating a resource allocation according to an embodiment of thepresent invention.

The first wireless communication terminal may transmit a reception readyframe and then transmit a resource allocation frame after apredetermined time. At this time, the predetermined time may be SIFSdefined in the 802.11 standard.

The reception ready frame may be in a format supported by a legacywireless communication terminal that does not support an embodiment ofthe present invention. This is because the reception ready frame is forsetting the NAV of the legacy wireless communication terminal as well asa wireless communication terminal supporting an embodiment of thepresent invention. In addition, the resource allocation frame may be ina format not supported by the legacy wireless communication terminal.Specifically, the first wireless communication terminal may use a higherMCS than the transmission of the reception ready frame in order fortransmission of the resource allocation frame. This is because thelegacy wireless communication terminal does not affect the datatransmission of the second wireless communication terminal even if thelegacy wireless communication terminal can not receive the resourceallocation frame. Through this, it is possible to reduce the timerequired for transmission of resource allocation frames.

The first wireless communication terminal may signal information onresources allocated to each of the plurality of second wirelesscommunication terminals through a preamble of a physical frame includinga resource allocation frame, a MAC header of a resource allocationframe, and a payload of a resource allocation frame. Specifically, thesignaling field of the physical frame including the resource allocationframe may indicate hierarchical information on the granularity of thefrequency bandwidth. In addition, the signaling field of the physicalframe including the resource allocation frame may indicate a groupidentifier for identifying a group including a plurality of secondwireless communication terminals that are to transmit data through agroup address field indicating a group address. At this time, thesignaling field may be an HE-SIG field, which is a signaling field for awireless communication terminal supporting an embodiment of the presentinvention. Specifically, the signaling field may be an HE-SIG A fieldfor signaling information commonly applied to a plurality of secondwireless communication terminals.

Also, the first wireless communication terminal may signal an identifierfor identifying the second wireless communication terminal and thebandwidth of the frequency band allocated to the second wirelesscommunication terminal through at least one of the MAC header, thepayload, and the HE-SIG B field of the resource allocation frame. Atthis time, the HE-SIG B field is a signaling field of a physical framefor signaling information applied to each of the plurality of secondwireless communication terminals.

According to a specific embodiment, the first wireless communicationterminal may signal all information of the resource allocation for thesecond wireless communication through the preamble of the physical frameincluding the resource allocation frame.

Accordingly, the second wireless communication terminal may obtaininformation on resources allocated to each of the plurality of secondwireless communication terminals through a preamble of a physical frameincluding a resource allocation frame, a MAC header of a resourceallocation frame, and a payload of a resource allocation frame.Specifically, the second wireless communication terminal may obtain anidentifier for identifying the second wireless communication terminaland information on the bandwidth of the frequency band allocated to thesecond wireless communication terminal through at least one of the MACheader, the payload, and the HE-SIG B field of the resource allocationframe. Also, according to a specific embodiment, the second wirelesscommunication terminal may obtain all the information of the resourceallocation for the second wireless communication through the preamble ofthe physical frame.

In a specific embodiment, the second wireless communication terminal maytransmit the channel state detected by the second wireless communicationterminal to the first wireless communication terminal as describedabove. Specifically, the second wireless communication terminal maytransmit the channel state detected by the second wireless communicationterminal to the first wireless communication terminal using theorthogonal code as described above.

In a specific embodiment, after receiving the resource allocation frame,the second wireless communication terminal may transmit the transmissionnotifying frame of the second wireless communication terminal. Throughthis, the second wireless communication terminal may set the NAV of awireless communication terminal located in the wireless communicationcoverage of the second wireless communication terminal.

In another specific embodiment, the second wireless communicationterminal may not transmit the transmission notifying frame of the secondwireless communication terminal. In such a case, the time required forthe second wireless communication terminal to transmit the receptionready frame may be saved. However, there is a risk that wirelesscommunication terminals located outside the wireless communicationcoverage of the first wireless communication terminal and within thewireless communication coverage of the second wireless communicationterminal may access the frequency band used by the second wirelesscommunication terminal.

The specific operations of the first wireless communication terminal andthe second wireless communication terminal will be described withreference to FIG. 16.

In the embodiment of FIG. 16, the access point AP transmits a CTS frameindicating reception preparation. At this time, the RA of the CTS framemay be a group address indicating a plurality of second wirelesscommunication terminals. Through this, the access point AP sets the NAVof a wireless communication terminal located in the wirelesscommunication coverage of the access point AP.

The access point AP transmits a resource allocation frame to theplurality of second wireless communication terminals. Specifically, theaccess point AP transmits a resource allocation frame after apredetermined time from transmission of the CTS frame. The structure ofthe resource allocation frame may be the same as one described above.

The first station STA1 to the fourth station STA4 obtain information ona frequency band allocated to each of the first station STA1 and thefourth station STA4 based on the resource allocation frame.

The first station STA1 to the fourth station STA4 transmit data througha frequency band allocated to each of the first station STA1 and thefourth station STA4.

The access point AP transmits an ACK frame to the first station STA1 tothe fourth station STA4. The access point AP may transmit an ACK frameto the first station STA1 to the fourth station STA4 through variousembodiments including the above-described embodiment.

In the embodiment of FIG. 16, the first wireless communication terminaltransmits a reception ready frame and then transmits a resourceallocation frame after a predetermined time. In such a case, it takes aconsiderable time for the first wireless communication terminal totransmit the resource allocation frame. Therefore, there is a need for amethod for reducing the time required for the first wirelesscommunication terminal to transmit a resource allocation frame. Thiswill be described with reference to FIGS. 17 and 18.

FIG. 17 is a view illustrating that an access point according to anotherembodiment of the present invention transmits a reception ready frameand a frame indicating resource allocation without time interval.

The first wireless communication terminal may transmit a reception readyframe and transmit a resource allocation frame without a time interval.Specifically, the first wireless communication terminal may transmit thereception ready frame immediately after the FCS field of the receptionready frame. At this time, the FCS field indicates whether the frameincludes error data.

In such a case, a wireless communication terminal that does not supportan embodiment of the present invention decodes the Frame Check Sequence(FCS) field of the reception ready frame, and enters a waiting state.The second wireless communication terminal supporting an embodiment ofthe present invention decodes the FCS field of the reception ready frameand then receives the resource allocation frame. At this time, thesecond wireless communication terminal supporting the embodiment of thepresent invention may determine whether the resource allocation frame istransmitted immediately after the FCS field of the reception ready framethrough the RA of the reception ready frame. For example, when the groupaddress indicating the plurality of second wireless communicationterminals is the RA of the reception ready frame, the second wirelesscommunication terminal may determine that the resource allocation frameis transmitted immediately after the FCS field of the reception readyframe.

In a specific embodiment, the second wireless communication terminal maytransmit the channel state detected by the second wireless communicationterminal to the first wireless communication terminal as describedabove. Specifically, the second wireless communication terminal maytransmit the channel state detected by the second wireless communicationterminal to the first wireless communication terminal using theorthogonal code as described above.

In a specific embodiment, after receiving the resource allocation frame,the second wireless communication terminal may transmit the transmissionnotifying frame of the second wireless communication terminal. Throughthis, the second wireless communication terminal may set the NAV of awireless communication terminal located in the wireless communicationcoverage of the second wireless communication terminal.

In another specific embodiment, the second wireless communicationterminal may not transmit the transmission notifying frame of the secondwireless communication terminal. In such a case, the time required forthe second wireless communication terminal to transmit the receptionready frame may be saved. However, there is a risk that wirelesscommunication terminals located outside the wireless communicationcoverage of the first wireless communication terminal and within thewireless communication coverage of the second wireless communicationterminal may access the frequency band used by the second wirelesscommunication terminal.

The specific operations of the first wireless communication terminal andthe second wireless communication terminal will be described withreference to FIG. 17.

In the embodiment of FIG. 17, the access point AP transmits a CTS frameand then immediately transmits a resource allocation frame. Thestructure of the resource allocation frame may be the same as onedescribed above.

The first station STA1 to the fourth station STA4 obtain information ona frequency band allocated to each of the first station STA1 and thefourth station STA4 based on the resource allocation frame.

The first station STA1 to the fourth station STA4 transmit data througha frequency band allocated to each of the first station STA1 and thefourth station STA4.

The access point AP transmits an ACK frame to the first station STA1 tothe fourth station STA4. The access point AP may transmit an ACK frameto the first station STA1 to the fourth station STA4 through variousembodiments including the above-described embodiment.

FIG. 18 is a view illustrating that an access point according to anotherembodiment of the present invention transmits one frame where atransmission notifying frame and a resource allocation frame areintegrated.

The first wireless communication terminal may indicate that the firstwireless communication terminal is ready to receive data and maytransmit an integrated frame for signaling resources allocated to eachof the plurality of second wireless communication terminals.

At this time, the RA of the integrated frame may be a group addressindicating a plurality of second wireless communication terminals.

Since the integrated frame indicates that the first wirelesscommunication terminal is ready to receive data, a legacy wirelesscommunication terminal that does not support an embodiment of thepresent invention should be able to receive the integrated frame and setthe NAV. For this, the integrated frame may include information onresource allocation for each of the plurality of second wirelesscommunication terminals, in the extension form of an MAC header. Inanother specific embodiment, the integrated frame may includeinformation on resource allocation for each of the plurality of secondwireless communication terminals, in the payload form of a frame. Inanother specific embodiment, the integrated frame may includeinformation on resource allocation for each of the plurality of secondwireless communication terminals, in the extension field form followingthe FCS field.

The second wireless communication terminal obtains information on aresource allocated to the second wireless communication terminal basedon the integrated frame.

In addition, a wireless communication terminal that receives theintegrated frame sets the NAV regardless of whether it is a legacywireless communication terminal and a wireless communication terminalsupporting an embodiment of the present invention.

In a specific embodiment, the second wireless communication terminal maytransmit the channel state detected by the second wireless communicationterminal to the first wireless communication terminal as describedabove. Specifically, the second wireless communication terminal maytransmit the channel state detected by the second wireless communicationterminal to the first wireless communication terminal using theorthogonal code as described above.

In a specific embodiment, after receiving the resource allocation frame,the second wireless communication terminal may transmit the transmissionnotifying frame of the second wireless communication terminal. Throughthis, the second wireless communication terminal may set the NAV of awireless communication terminal located in the wireless communicationcoverage of the second wireless communication terminal.

In another specific embodiment, the second wireless communicationterminal may not transmit the transmission notifying frame of the secondwireless communication terminal. In such a case, the time required forthe second wireless communication terminal to transmit the receptionready frame may be saved. However, there is a risk that wirelesscommunication terminals located outside the wireless communicationcoverage of the first wireless communication terminal and within thewireless communication coverage of the second wireless communicationterminal may access the frequency band used by the second wirelesscommunication terminal.

The specific operations of the first wireless communication terminal andthe second wireless communication terminal will be described withreference to FIG. 18.

In the embodiment of FIG. 18, the access point AP transmits theabove-mentioned integrated frame. Through this, a wireless communicationterminal located in the wireless communication coverage of the accesspoint AP sets an NAV. The structure of the integrated frame may be thesame as one described above.

The first station STA1 to the fourth station STA4 obtain information onallocated frequency bands based on the integrated frame.

The first station STA1 to the fourth station STA4 transmit data throughan allocated frequency band.

The access point AP transmits an ACK frame to the first station STA1 tothe fourth station STA4. The access point AP may transmit an ACK frameto the first station STA1 to the fourth station STA4 through variousembodiments including the above-described embodiment.

It is described with reference to FIGS. 19 and 20 that the firstwireless communication terminal transmits a reception completion frameto the plurality of second wireless communication terminals.

FIG. 19 is a view illustrating that when not receiving data through anyone sub-frequency band, an access point transmits an ACK frame accordingto another embodiment of the present invention.

As described above, the first wireless communication terminal mayreceive data and transmit a reception completion frame to each of theplurality of second wireless communication terminals that transmit thedata. Specifically, the first wireless communication terminal maytransmit a reception completion frame to the second wirelesscommunication terminal through a frequency band having a minimumfrequency bandwidth allocable to the second wireless communicationterminal. The minimum frequency bandwidth that the first wirelesscommunication terminal is able to allocate to the second wirelesscommunication terminal may be the smallest unit of the sub-carrierblock.

In such a case, the first wireless communication terminal may transmittransmission completion frames to the plurality of wirelesscommunication terminals at once. However, for compatibility with alegacy wireless communication terminal, the first wireless communicationterminal may transmit the reception completion frame again through thefrequency band having more than the minimum unit frequency bandwidth. Atthis time, the RA of the reception completion frame may be a groupaddress indicating a plurality of second wireless communicationterminals. In another specific embodiment, the RA of the receptioncompletion frame may be the address of the first wireless communicationterminal.

Also, the first wireless communication terminal may transmit thereception completion frame only through the frequency band in which thedata is transmitted. The first wireless communication terminal may nottransmit the reception completion frame in the frequency-band where nodata is transmitted.

The specific operations of the first wireless communication terminal andthe second wireless communication terminal will be described withreference to FIG. 19.

In the embodiment of FIG. 19, the access point AP allocates a resourceto each of the first station STA1 to the fourth station STA4.

The access point AP transmits a CTS frame having the group addressindicating the first station STA1 to the second station STA4 as an RA.Through this, the access point AP sets the NAV of a wirelesscommunication terminal located in the wireless communication coverage ofthe access point AP.

The access point AP transmits a resource allocation frame for signalinga resource allocated to each of the first station STA1 to the secondstation STA4.

Each of the first station STA1 to the fourth station STA4 obtainsinformation on a resource allocated to each of the first station STA1 tothe fourth station STA4 based on the resource allocation frame.

The first station STA1 to the fourth station STA4 transmit to the accesspoint AP a CTS frame for notifying that the data is to be transmittedsimultaneously. As described above, the transmission address of the CTSframe may be a group address indicating a group including the firststation STA2 to the fourth station STA4. Through this, the first stationSTA1 to the fourth station STA4 set the NAV of a wireless communicationterminal located in the wireless coverage of the first station STA1 tothe fourth station STA4.

The second station STA2 to the fourth station STA4 transmit data to theaccess point AP through a resource allocated to each.

The access point AP receives data from the second station STA2 to thefourth station STA4 through the resources allocated to the secondstation STA2 to the fourth station STA4, respectively.

The access point AP transmits an ACK frame indicating completion ofreception to each of the second station STA2 to the fourth station STA4through the channel allocated to each of the second station STA2 to thefourth station STA4. At this time, since the access point AP does notreceive data from the first station STA1, the access point AP does nottransmit an ACK frame through the channel allocated to the first stationSTA1.

The access point AP transmits an ACK frame having a group addressindicating the group including the second station to the fourth stationas an RA through the entire channel having the minimum unit frequencybandwidth.

Through such an embodiment, the first wireless communication terminalmay reduce the time required for transmission of the receptioncompletion frame. However, in such a case, for compatibility with alegacy wireless communication terminal, the transmission completionframe should be transmitted again through the frequency band having theminimum frequency unit bandwidth.

A reception completion frame indicating whether reception of datatransmitted by a plurality of second wireless communication terminals iscompleted will be described with reference to FIG. 20.

FIG. 20 is a view illustrating that an access point according to anotherembodiment of the present invention transmits an ACK frame andillustrating the syntax of the ACK frame.

The first wireless communication terminal may transmit a multi-terminalreception completion frame indicating whether reception of datatransmitted by the plurality of second wireless communication terminalsis completed.

Specifically, the first wireless communication terminal maysimultaneously transmit a plurality of different multi-terminalreception completion frames for each minimum unit frequency bandwidth.In a specific embodiment, the first wireless communication terminal maysimultaneously transmit a plurality of multi-terminal receptioncompletion frames through OFDMA. At this time, the first wirelesscommunication terminal may transmit a multi-terminal receptioncompletion frame through a wireless frequency band allocated to theplurality of second wireless communication terminals that are to receivethe corresponding multi-terminal reception completion frame. Forexample, the first wireless communication terminal may transmit thefirst multi-terminal reception completion frame and the secondmulti-terminal reception completion frame as one physical frame throughOFDMA. At this time, the first wireless communication terminal maytransmit a first multi-terminal reception completion frame to the secondwireless communication terminal of the first group through the frequencyband allocated to the second wireless communication terminal of thefirst group. Here, the first group represents a plurality of secondwireless communication terminals that are to receive the firstmulti-terminal reception completion frame. In addition, the firstwireless communication terminal may transmit a second multi-terminalreception completion frame to the second wireless communication terminalof the second group through the frequency band allocated to the secondwireless communication terminal of the second group. Here, the secondgroup represents a plurality of second wireless communication terminalsthat are to receive the second multi-terminal reception completionframe.

In another specific embodiment, the first wireless communicationterminal may consider compatibility with a legacy wireless communicationterminal that does not support an embodiment of the present inventionwhen transmitting a reception completion frame. Accordingly, themulti-terminal reception completion frame may be the same as thetransmission complete frame format supported by the legacy communicationterminal. In addition, the first wireless communication terminal maytransmit a multi-terminal reception completion frame through a frequencyband having a minimum unit frequency bandwidth.

The multi-terminal reception completion frame may include an identifierfor identifying a plurality of second wireless communication terminals.At this time, the identifier for identifying the plurality of secondwireless communication terminals may be a group address indicating agroup including a plurality of second wireless communication terminals.In a specific embodiment, the RA of the multi-terminal receptioncompletion frame may be a group address indicating a group including aplurality of second wireless communication terminals.

The multi-terminal reception completion frame may indicate that there isdata not received. Specifically, the multi-terminal reception completionframe may include a bit value indicating that there is data notreceived. In a specific embodiment, the multi-terminal receptioncompletion frame may indicate that data transmitted by any one secondwireless communication terminal is not received. In another specificembodiment, the multi-terminal reception completion frame may indicatewhether data reception is completed for each sub-frequency band of thefrequency band in which the multi-terminal reception completion frame istransmitted. Specifically, a field value indicating the RA of themulti-terminal reception completion frame may indicate whether the datareception is completed for each sub-frequency band of the frequency bandin which the multi-terminal reception completion frame is transmitted.For example, the address field of the multi-terminal receptioncompletion frame may be a 6-byte field. At this time, a 5-byte field maybe a group address indicating a group including a plurality of secondwireless communication terminals. Each of the eight bits included in theremaining one byte may indicate whether data received through eachsub-frequency band is received. For example, if the value of the bit is1, it may indicate that the first wireless communication terminalcompletely receives the data transmitted through the correspondingsub-frequency band. If the value of the bit is 0, it may indicate thatthe first wireless communication terminal does not completely receivethe data transmitted through the corresponding sub-frequency band.

Accordingly, the first wireless communication terminal sets the fieldvalue of the multi-terminal reception completion frame according towhether data is received or not.

The second wireless communication terminal determines whether the firstwireless communication terminal receives the data based on the fieldvalue of the multi-terminal reception completion frame.

The specific operations of the first wireless communication terminal andthe second wireless communication terminal will be described withreference to FIG. 20.

In the embodiment of FIG. 20, the access point AP allocates a resourceto each of the first station STA1 and the second station STA2.

The access point AP transmits a CTS frame having the group addressindicating the first station STA1 and the second station STA2 as an RA.Through this, the access point AP sets the NAV of a wirelesscommunication terminal located in the wireless communication coverage ofthe access point AP.

The access point AP transmits a resource allocation frame for signalinga resource allocated to each of the first station STA1 and the secondstation STA2.

The first station STA1 and the second station STA2 obtain information ona resource allocated to the first station STA1 and the second stationSTA2 based on the resource allocation frame.

The first station STA1 and the second station STA2 transmit to theaccess point AP a CTS frame for notifying that the data is to betransmitted simultaneously. As described above, the transmitter addressof the CTS frame may be a group address indicating a group including thefirst station STA2 and the second station STA2. In addition, the firststation STA1 and the second station STA2 transmit the CTS frame to theaccess point AP using the same data rate and the same scramble seed. Thefirst station STA1 sets the NAV of a wireless communication terminallocated in the wireless coverage of the first station STA1 and thesecond station STA2 sets the NAV of a wireless communication terminallocated in the wireless coverage of the second station STA2.

The first station STA1 and the second station STA2 transmit data to theaccess point AP through a resource allocated to each.

The access point AP receives data from the first station STA1 and thesecond station STA2 through the resources allocated to the first stationSTA1 and the second station STA2, respectively.

The access point AP transmits a multi-terminal ACK frame indicatingcompletion of reception by the first station STA1 and the second stationSTA2. Specifically, the multi-terminal ACK frame may include a groupaddress indicating a group including a first station STA1 and a secondstation STA2. Also, since the access point AP receives data through allthe sub-frequency bands, the value of the 8-bit field indicatingcompletion of reception of the multi-terminal ACK frame may be all 1s.

Through such an operation, it is possible to reduce the time requiredfor the first wireless communication terminal to transmit thetransmission completion frame to a plurality of second wirelesscommunication terminals.

FIG. 21 is a ladder diagram illustrating operations of a first wirelesscommunication terminal and a second wireless communication terminalaccording to an embodiment of the present invention.

The first wireless communication terminal 400 transmits a receptionready frame indicating that it is ready to receive data to the secondwireless communication terminal (S2501). The first wirelesscommunication terminal 400 may transmit a reception ready frame to theplurality of second wireless communication terminals 500 through acontention-based access using a back-off. Specifically, when the channelis idle for a predetermined time, the first wireless communicationterminal 400 may transmit a reception ready frame to the plurality ofsecond wireless communication terminals 500. At this time, thepredetermined time may be an arbitration inter-frame space (AIFS) or aDCF inter-frame space (DIFS) defined in the 802.11 standard.

The reception ready frame may follow the RTS frame format defined by the802.11 standard. However, when the reception ready frame is in the RTSframe format, a wireless communication terminal included in the wirelesscommunication coverage of the first wireless communication terminal butnot included in the wireless communication coverage of the secondwireless communication terminal may determine that the RTS frame istimeout before the ACK frame transmission time point of the firstwireless communication terminal.

Therefore, the reception ready frame may follow the CTS frame formatdefined by the 802.11 standard. Especially, the reception ready framemay be a CTS frame whose Receiver Address (RA) is the address of thefirst wireless communication terminal that transmits the CTS frame. Inaddition, the RA of the reception ready frame may be a group addressindicating a plurality of second wireless communication terminals.

The first wireless communication terminal 400 transmits a resourceallocation frame indicating information on the resources allocated tothe plurality of second wireless communication terminals 500 to thesecond wireless communication terminal (S2503). The first wirelesscommunication terminal 400 may receive information on the channel statedetected by each of the plurality of second wireless communicationterminals 500 from each of the plurality of second wirelesscommunication terminals 500. At this time, the first wirelesscommunication terminal 400 may allocate a resource to each of theplurality of second wireless communication terminals 500 based on theinformation on the channel state detected by each of the plurality ofsecond wireless communication terminals 500. Specifically, the firstwireless communication terminal 400 may allocate a frequency band toeach of the plurality of second wireless communication terminals 500based on the information on the channel state detected by each of theplurality of second wireless communication terminals 500.

At this time, the second wireless communication terminal 500 may performtransmission using the orthogonal code as described above. Theorthogonal code may be any one of a plurality of orthogonal codes. Inanother specific embodiment, the second wireless communication terminal500 may use a fixed orthogonal code. Specifically, the fixed orthogonalcode may be allocated to the second wireless communication terminal 500when the first wireless communication terminal 400 and the secondwireless communication terminal 500 are associated. In addition, thefixed orthogonal code may be re-allocated to the second wirelesscommunication terminal 500 when the first wireless communicationterminal 400 and the second wireless communication terminal 500 areassociated again. At this time, the fixed orthogonal code may beobtained by calculating the identifier of the second wirelesscommunication terminal 500 with the size and module of the orthogonalcode set. At this time, the identifier of the second wirelesscommunication terminal 500 may be an AID for identifying the associationof the first wireless communication terminal 400 and the second wirelesscommunication terminal 500.

The second wireless communication terminal 500 may transmit a signalmodulated using the orthogonal code to the first wireless communicationterminal 400 through all the channels detected as idle.

The second wireless communication terminal 500 may receive informationon a channel to be detected by the first wireless communication terminal400 and may detect a channel state based on information on the channelto be detected. At this time, the reception ready frame may signalinformation on a channel whose state is to be detected by the firstwireless communication terminal 400. Specifically, the RA value of thereception ready frame may indicate information on a channel whose stateis to be detected by the first wireless communication terminal.

In addition, the first wireless communication terminal 400 may transmitthe resource allocation frame through the frequency band allocated tothe second wireless communication terminal 500. At this time, if thefrequency band allocated to each of the plurality of second wirelesscommunication terminals 500 is smaller than the minimum unit frequencyband, the first wireless communication terminal 400 may transmit theresource allocation frame to the second wireless communication terminal500 through the frequency band having a frequency bandwidth smaller thanthe minimum unit frequency bandwidth. In a specific embodiment, thefirst wireless communication terminal 400 may transmit a resourceallocation frame to the second wireless communication terminal 500through a frequency band having a minimum frequency bandwidth allocableto the second wireless communication terminal 500. The minimum frequencybandwidth that the first wireless communication terminal 400 is able toallocate to the second wireless communication terminal 500 may be thesmallest unit of the sub-carrier block.

As described above, the first wireless communication terminal 400 maysignal information on resources allocated to each of the plurality ofsecond wireless communication terminals 500 through a preamble of aphysical frame including a resource allocation frame, a MAC header of aresource allocation frame, and a payload of a resource allocation frame.

In addition, the first wireless communication terminal 400 may transmita reception ready frame and then transmit a resource allocation frameafter a predetermined time. At this time, the predetermined time may beSIFS defined in the 802.11 standard.

In another specific embodiment, the first wireless communicationterminal 400 may transmit a reception ready frame and transmit aresource allocation frame without a time interval. Specifically, thefirst wireless communication terminal 400 may transmit the receptionready frame immediately after the FCS field of the reception readyframe. At this time, the FCS field indicates whether the frame includeserror data.

In another specific embodiment, the first wireless communicationterminal may indicate that it is ready to receive data and may transmitan integrated frame for signaling resources allocated to each of theplurality of second wireless communication terminals. In a specificembodiment, the integrated frame may include information on resourceallocation for each of the plurality of second wireless communicationterminals 500 in the extension form of an MAC header. In anotherspecific embodiment, the integrated frame may include information onresource allocation for each of the plurality of second wirelesscommunication terminals 500 in the payload form of a frame. In anotherspecific embodiment, the integrated frame may include information onresource allocation for each of the plurality of second wirelesscommunication terminals 500 in the extension field form following theFCS field.

The second wireless communication terminal 500 obtains information onthe allocated resource based on the resource allocation frame (S2505).

The second wireless communication terminal 500 transmits a transmissionnotifying frame for notifying the transmission of the second wirelesscommunication terminal 500 to the first wireless communication terminal400 (S2507). The transmission notifying frame sets the NAV of a wirelesscommunication terminal located in the wireless communication coverage ofthe second wireless communication terminal 500.

The plurality of second wireless communication terminals 500 maytransmit a transmission notifying frame to the first wirelesscommunication terminal 400 at the same time. Specifically, the pluralityof second wireless communication terminals 500 may simultaneouslytransmit the transmission notifying frame including the same format andthe same contents. At this time, the transmission address of thetransmission notifying frame may be a group address indicating aplurality of second wireless communication terminals 500.

In addition, the plurality of second wireless communication terminals500 may simultaneously transmit the transmission notifying frame usingthe same data rate and scramble seed. Specifically, the plurality ofsecond wireless communication terminals 500 may simultaneously transmita transmission notifying frame based on an MCS or a data rate of areception ready frame. In another specific embodiment, the plurality ofsecond wireless communication terminals 500 may simultaneously transmitthe transmission notifying frame based on the MCS or the data rate ofthe resource allocation frame. In such a case, even if the plurality ofsecond wireless communication terminals simultaneously transmit thetransmission notifying frame, collision does not occur betweentransmission notifying frames.

The transmission notifying frame may be in a format receivable by alegacy wireless communication terminal that does not support anembodiment of the present invention. Therefore, the second wirelesscommunication terminal 500 may transmit the transmission notifying framethrough the frequency band having the minimum unit frequency bandwidth.At this time, the minimum unit frequency bandwidth represents a minimumbandwidth used by the first wireless communication terminal 400.Specifically, the second wireless communication terminal 500 may have afrequency band allocated to the second wireless communication terminal500 and transmit the transmission notifying frame through the frequencyband having the minimum unit frequency band. In another specificembodiment, the second wireless communication terminal 500 may transmita transmission notifying frame through a primary channel having aminimum unit frequency bandwidth. In a specific embodiment, the minimumunit frequency bandwidth may be 20 MHz.

In another specific embodiment, the second wireless communicationterminal 500 may transmit a transmission notifying frame through afrequency band allocated to the second wireless communication terminal.

In a specific embodiment, the transmission notifying frame may be a CTSframe.

In addition, if there is a frequency band that does not receive thetransmission notifying frame, the first wireless communication terminal400 may reset the NAV set in the corresponding frequency band.Specifically, if there is a frequency band in which the transmissionnotifying frame is not received, the first wireless communicationterminal 400 may transmit the NAV reset frame indicating that the NAVset in the frequency band in which the frame is transmitted through thecorresponding frequency band. Specifically, if all of the secondwireless communication terminals 500 to which sub-frequency bandsincluded in any one frequency band (channel) are allocated, are not ableto transmit the transmission notifying frame, the first wirelesscommunication terminal 400 may transmit the NAV reset frame through thecorresponding frequency band. At this time, the NAV reset frame may be aCF-END frame.

The second wireless communication terminal 500 transmits data to thefirst wireless communication terminal 400 through the resource allocatedto the second wireless communication terminal 500 (S2509). Specifically,the second wireless communication terminal 500 may transmit data to thefirst wireless communication terminal 400 through the resource allocatedto the second wireless communication terminal 500.

The first wireless communication terminal 400 transmits a receptioncompletion frame indicating that the data is received from the pluralityof second wireless communication terminals 500 to the second wirelesscommunication terminal 500 (S2511).

As described above, the first wireless communication terminal 400 mayreceive data and transmit the reception completion frame to each of theplurality of second wireless communication terminals 500 that transmitsthe data. Specifically, the first wireless communication terminal 400may transmit a reception completion frame to the second wirelesscommunication terminal through a frequency band having a minimumfrequency bandwidth allocated to the second wireless communicationterminal 500. In a specific embodiment, the first wireless communicationterminal 400 may transmit a reception completion frame to each of theplurality of second wireless communication terminals 500 for eachfrequency band allocated to each of the plurality of second wirelesscommunication terminals 500 through OFDMA. At this time, the frequencyband allocated to the second wireless communication terminal 500 may bethe minimum frequency bandwidth that the first wireless communicationterminal 400 is able to allocate to the second wireless communicationterminal 500.

The minimum frequency bandwidth that the first wireless communicationterminal 400 is able to allocate to the second wireless communicationterminal 500 may be the smallest unit of the sub-carrier block.

In addition, the first wireless communication terminal 400 may transmita reception completion frame for each minimum frequency bandwidth thatthe first wireless communication terminal 400 is able to allocate to thesecond wireless communication terminal 500. In such a case, thereception completion frame may indicate that data is received throughthe frequency band in which the reception completion frame istransmitted.

In such a case, the first wireless communication terminal 400 maytransmit transmission completion frames to the plurality of wirelesscommunication terminals at once. However, for compatibility with alegacy wireless communication terminal, the first wireless communicationterminal may transmit the reception completion frame again through thefrequency band having the minimum unit frequency bandwidth. At thistime, the RA of the reception completion frame may be a group addressindicating a plurality of second wireless communication terminals. Inanother specific embodiment, the RA of the reception completion framemay be the address of the first wireless communication terminal 400.

Also, the first wireless communication terminal 400 may transmit areception completion frame only through a frequency band in which datais transmitted. The first wireless communication terminal 400 may nottransmit a reception completion frame to a frequency-band in which datais not transmitted.

Also, the first wireless communication terminal 400 may transmit amulti-terminal reception completion frame indicating whether the datatransmitted by the plurality of second wireless communication terminals500 is received completely as a reception completion frame.

Specifically, the first wireless communication terminal 400 maysimultaneously transmit a plurality of different multi-terminalreception completion frames for each minimum unit frequency bandwidth.In a specific embodiment, the first wireless communication terminal 400may simultaneously transmit a plurality of multi-terminal receptioncompletion frames through OFDMA. At this time, the first wirelesscommunication terminal 400 may transmit a multi-terminal receptioncompletion frame through a wireless frequency band allocated to theplurality of second wireless communication terminals 500 that are toreceive the corresponding multi-terminal reception completion frame. Forexample, the first wireless communication terminal 400 may transmit thefirst multi-terminal reception completion frame and the secondmulti-terminal reception completion frame as one physical frame throughOFDMA. At this time, the first wireless communication terminal 400 maytransmit a first multi-terminal reception completion frame to the secondwireless communication terminal 400 of the first group through thefrequency band allocated to the second wireless communication terminal500 of the first group. Here, the first group represents a plurality ofsecond wireless communication terminals 500 that are to receive thefirst multi-terminal reception completion frame. In addition, the firstwireless communication terminal 400 may transmit a second multi-terminalreception completion frame to the second wireless communication terminal500 of the second group through the frequency band allocated to thesecond wireless communication terminal 500 of the second group. Here,the second group represents a plurality of second wireless communicationterminals 500 that are to receive the second multi-terminal receptioncompletion frame.

As described above, the first wireless communication terminal 400 mayconsider compatibility with a legacy wireless communication terminalthat does not support an embodiment of the present invention whentransmitting a reception completion frame. Accordingly, themulti-terminal reception completion frame may be the same as thetransmission complete frame format supported by the legacy communicationterminal. In addition, the first wireless communication terminal 400 maytransmit a multi-terminal reception completion frame through a frequencyband having a minimum unit frequency bandwidth.

The multi-terminal reception completion frame may include an identifierfor identifying a plurality of second wireless communication terminals500. At this time, the identifier for identifying the plurality ofsecond wireless communication terminals 500 may be a group addressindicating a group including a plurality of second wirelesscommunication terminals 500. In a specific embodiment, the RA of themulti-terminal reception completion frame may be a group addressindicating a group including a plurality of second wirelesscommunication terminals 500.

The multi-terminal reception completion frame may indicate that there isdata not received. Specifically, the multi-terminal reception completionframe may include a bit value indicating that there is data notreceived. In a specific embodiment, the multi-terminal receptioncompletion frame may indicate that data transmitted by any one secondwireless communication terminal 500 is not received. In another specificembodiment, the multi-terminal reception completion frame may indicatewhether data reception is completed for each sub-frequency band of thefrequency band in which the multi-terminal reception completion frame istransmitted. Specifically, a field value indicating the RA of themulti-terminal reception completion frame may indicate whether the datareception is completed for each sub-frequency band of the frequency bandin which the multi-terminal reception completion frame is transmitted.For example, the address field of the multi-terminal receptioncompletion frame may be a 6-byte field. At this time, a 5-byte field maybe a group address indicating a group including a plurality of secondwireless communication terminals. Each of the eight bits included in theremaining one byte may indicate whether data received through eachsub-frequency band is received. For example, if the value of the bit is1, it may indicate that the first wireless communication terminal 400completely receives the data transmitted through the correspondingsub-frequency band. If the value of the bit is 0, it may indicate thatthe first wireless communication terminal 400 does not completelyreceive the data transmitted through the corresponding sub-frequencyband. Accordingly, the first wireless communication terminal 400 setsthe field value of the multi-terminal reception completion frameaccording to whether data is received or not. The second wirelesscommunication terminal 500 determines whether the first wirelesscommunication terminal receives the data based on the field value of themulti-terminal reception completion frame.

Although the present invention is described by using wireless LANcommunication as an example, it is not limited thereto and may beapplied to other communication systems such as cellular communication.Additionally, while the method, device, and system of the presentinvention are described in relation to specific embodiments thereof,some or all of the components or operations of the present invention maybe implemented using a computer system having a general purpose hardwarearchitecture.

The features, structures, and effects described in the above embodimentsare included in at least one embodiment of the present invention and arenot necessary limited to one embodiment. Furthermore, features,structures, and effects shown in each embodiment may be combined ormodified in other embodiments by those skilled in the art. Therefore, itshould be interpreted that contents relating to such combination andmodification are included in the range of the present invention.

While the present invention is described mainly based on the aboveembodiments but is not limited thereto, it will be understood by thoseskilled in the art that various changes and modifications are madewithout departing from the spirit and scope of the present invention.For example, each component specifically shown in the embodiments may bemodified and implemented. It should be interpreted that differencesrelating to such modifications and application are included in the scopeof the present invention defined in the appended claims.

1-20. (canceled)
 21. A wireless communication terminal comprising: atransceiver; and a processor, wherein the processor is configured to:receive, by using the transceiver, a Medium Access Control (MAC) framewhich triggers a simultaneous uplink transmission of a plurality ofwireless communication terminals including the wireless communicationterminal, from a base wireless communication terminal, wherein the MACframe indicates whether a clear channel assessment (CCA) is required ina channel, perform the CCA in the channel in response to receiving theMAC frame when the MAC frame indicates the CCA is required in thechannel, and transmit, based on whether the channel is sensed to be idleby the CCA, a response MAC frame for the MAC frame to the base wirelesscommunication terminal in the channel.
 22. The wireless communicationterminal of claim 21, wherein the processor is configured to perform theCCA in unit of 20 MHz.
 23. The wireless communication terminal of claim21, wherein the channel is a secondary channel.
 24. The wirelesscommunication terminal of claim 21, wherein the MAC frame includesinformation on a channel in which the CCA to be performed, wherein theprocessor is configured to perform the CCA according to the information.25. The wireless communication terminal of claim 21, wherein a timepoint when the response MAC frame is transmitted is determined based ona short inter-frame space (SIFS), wherein the SIFS is applied in thesimultaneous uplink transmission of the plurality of wirelesscommunication terminals.
 26. A base wireless communication terminalcomprising: a transceiver; and a processor, wherein the processor isconfigured to: transmit, by using the transceiver, a Medium AccessControl (MAC) frame which triggers a simultaneous uplink transmission ofa plurality of wireless communication terminals, to the plurality ofwireless communication terminals, wherein the MAC frame indicateswhether a clear channel assessment (CCA) is required in at least onechannel, and receive at least one response MAC frame for the MAC framefrom at least one of the plurality of wireless communication terminalsin at least one channel, wherein when the MAC frame indicates that theCCA is required in a channel in which the at least one response MACframe is transmitted, the at least one response MAC frame is transmittedbased whether the channel in which the at least one response MAC frameis transmitted is sensed to be idle by the CCA, wherein the CCA isperformed by a wireless communication terminal which transmit the atleast one response MAC frame among the plurality of wirelesscommunication terminals.
 27. The base wireless communication terminal ofclaim 26, wherein the CCA is performed in unit of 20 MHz.
 28. The basewireless communication terminal of claim 26, the CCA is performed in asecondary channel based on the MAC frame.
 29. The base wirelesscommunication terminal of claim 26, wherein the processor is configuredto insert information on a channel in which the CCA to be performed intothe MAC frame.
 30. The base wireless communication terminal of claim 26,wherein a time point when the response MAC frame is received isdetermined based on a short inter-frame space (SIFS), wherein the SIFSis applied in the simultaneous uplink transmission of the plurality ofwireless communication terminals.
 31. An operating method of a wirelesscommunication terminal comprising: receiving a Medium Access Control(MAC) frame which triggers a simultaneous uplink transmission of aplurality of wireless communication terminals including the wirelesscommunication terminal, from a base wireless communication terminal,wherein the MAC frame indicates whether a clear channel assessment (CCA)is required in a channel, performing the CCA in at least one of channelsin response to receiving the MAC frame when the MAC frame indicates theCCA is required in the channel, and transmitting, based on whether thechannel is sensed to be idle by the CCA, a response MAC frame for theMAC frame to the base wireless communication terminal in the channel.32. The method of claim 31, wherein the performing the CCA comprisesperforming the CCA in unit of 20 MHz.
 33. The method of claim 31,wherein the channel is a secondary channel.
 34. The method of claim 31,wherein the MAC frame includes information on a channel in which the CCAto be performed, wherein the performing the CCA comprises performing theCCA according to the information.
 35. The method of claim 31, wherein atime point when the response MAC frame is transmitted is determinedbased on a short inter-frame space (SIFS), wherein the SIFS is appliedin the simultaneous uplink transmission of the plurality of wirelesscommunication terminals.